Consumer Power Quality Problems by mky16363

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									                      Consumer Power Quality Problems:
                        Troubleshooting by Telephone

                       Reprint of handbook edited and published by NRECA, 1999
              Text by François D. Martzloff, National Institute of Standards and Technology
                                      Graphics by Susan Spangler



Significance
Part 6: Tutorials, textbooks and reviews

This is a handbook developed for use by NRECA service representatives when dealing with
custom ers m aking com plaints over the telephone about power quality of their service, with a set of
questions work sheets that could help diagnose the problem without requiring distant travel by
service technicians, or to get them better prepared to do so.

The National Rural Electric Cooperative Association (NRECA) is the national service organization
of m ore than 900 rural electric system s. These cooperatively owned utilities own and operate
about 44% of the m iles of distribution lines in the nation to provide power to less than 10% of the
consum ers. NRECA is the national service nation's people, prim arily in the sparsely populated,
rural areas of 46 states. NRECA was founded in 1942 to unite rural electric system s in a way that
would perm it them to develop the services and support needed to properly serve rural Am erica.
NRECA is on of the largest, rural-oriented cooperative organizations in the United States.
           Prepared by

      National Rural Electric
     Cooperative Association
 Cooperative Research Network
     4301 Wilson Boulevard
 Arlington, Virginia 22203-1 860

               and

      Fran~oisD. Martzloff
National Institute of Standards and
            Technology
         100 Bureau Drive
 Gaithersburg, Maryland 20899




 &
 N
@C
COOPERATIVE RESEARCH NETWORK
The National rural Electric Cooperative Association (NRECA) is the national service organization of more than 900 rural electric
systems. These cooperatively owned utilities own and operate about 44% of the miles of distribution lines in the nation to pro-
vide power to less than 10% of the nation's people, primarily in the sparsely populated, rural areas of 46 states.
   NRECA was founded in 1942 to unite rural electric systems in a way that would permit them to develop the servlces and
support needed to properly serve rural America. NRECA is on of the largest, rural-oriented cooperative organizations in the
United States.
   The Cooperative Research Network, a service of NRECA that was used to support this project, was created to conduct studies
and carry out research of special interest to rural electric systems and thelr consumers.
                                                                          Contents   -   v




Section 1   Disturbances and Remedies
            Introduction
            The Nature of Disturbances
            Too Much Voltage
            Not Enough Voltage
            Other Power-Line Disturbances
            System Interactions


Section 2   Questions to Ask
            Customer-Owned Offenders
            How to Use the Worksheets
            Identifying Residential and Commercial Appliance Categories
            Worksheet EDE: Electronic, dual, external
            Worksheet EDI: Electronic, dual, internal
            Worksheet ES: Electronic, simple
            Worksheet HE: Heat, electron~c
            Worksheet HM: Heat, mechanical
            Worksheet ME: Motor, electronic
            Worksheet MM: Motor, mechanical
            Worksheet PLC: Power line conditioning
vi   -   Illustrations




ILLUSTRATIONS
                         FIGURE                                                                             PAGE


                         1.1                       C
                                  Sine wave of an A voltage supply.                                            2


                         1.2      A surge induced by lightning on an A voltage.
                                                                      C                                        3

                         1.3.     Typical voltage on a distribution bus during capacitor bank energizing.      4

                         1.4:     Example of a customer's bus voltage during utility capacitor switching.      5


                         1.5      A lamp and a rabbit-ear TV are examples of single-port appliances.           6
                                  A computer with a telephone modem connection is an example
                                  of a two-port appliance. An ordinary house offers many examples
                                  of both single-port and multiple-port appliances.


                         1.6      A typical WSS with power and telephone protection.                           7


                         1.7      A meter-base arrester installed by the utility.                              7


                         1.8      Relative energy deposited in the suppressor by a typical high-energy         9
                                  surge for various combinations of 250-volt (H), 150-volt (M), and
                                            L
                                  130-volt ( ) ratings, as a function of separation distance.


                                  Division of surge current in a cascade of two 150-volt devices: I,
                                  is the current in a 40-rnm-diameter arrester and I is the current in
                                                                                    ,
                                  a 20-mm-diameter suppressor, with 10-meter separation for the
                                  same 3000-ampere surge as in Figure 1.8.


                         1.10     A voltage swell lasting eight cycles.                                       10


                         1.11     Unequal line voltages caused by an open neutral.                            11


                         1.12     A very brief outage (top) and a very long outage (bottom).                  13


                         1.13     A sag lasting 10 cycles with the line voltage reduced to 55% of normal.     13


                         1.14     The original CBEMA curve (top) and the updated ITIC curve (bottom).         15


                         1-15     Noise superimposed on an AC voltage.                                        16
                                                                           Illustrations   -   vii




FIGURE                                                                                 PAGE
         -                  -   --    - .
                                     . -


1.16     An AC voltage distorted by harmonics.                                                 16

1.17     Commutation notches on an AC voltage.                                                 17


         Power and telephone services enter the house at opposite ends.
         A personal computer is connected across the two systems.


         Voltage and current recorded with telephone and power services                        19
         entering at opposite ends of the house.


1.20     Mitigation obtained by inserting a surge reference equalizer in
         both the power line and the telephone line.


1.21     Shifting reference potential can be remedied by inserting a surge                     21
         reference equalizer on the communications and power lines (here,
         the appliance is a TV and the communications line 1s a TV cable,
         but a PC with a telephone modem connection presents the same
         problem). In the ideal situation, the commun~cationsand power lines
         enter the house on the same side, and the SRE is most effective.
viii   -   Tables




                    TABLE                                                   PAGE


                    2.1     Home-Based Disturbances, Causes, and Remedies     23
                                                                              -

                    2.2     Categories of Equipment Victims                   25
                                                                                        Forward - ix




                                                                       FOREWORD
Customer service representatives have a tough         Senrice representatives can use the work-
task when they have to respond to calls from       sheets in conjunction with the manual's simple
consumers who are having problems with an          explanations of the nature of disturbances and
appliance. "My television won't work. What's       how to prevent or cure their effects to diagnose
wrong?" "My computer lost its memory. What         specific problems. On the basis of the diagnosis,
did the co-op d o to cause this?" Complaints may   the representative can tell the consumer what to
be couched in vague terms, and the caller may      d o or can call in the cooperative's repair service
tend to blame the electric cooperative.            to handle the problem. If the cause of a particu-
   This manual was commissioned by the             lar problem proves elusive, the representative
Cooperative Research Network to address these      can refer ir to a specialist.
kinds of complaints. Written with the help of         The manual should help representatives work
an expert in household and small-business elec-    more effectively and efficiently. It should help
tricity problems, it provides a series of work-    cooperatives avoid unnecessary service calls. And
sheets that guide representatives through a        it should help consumers get quick solutions to
question-and-answer session with a caller, lead-   their problems, whether utility-related or not.
ing the caller from the general to the specific
with the goal of finding the exact source of the     Martin E. Gordon, PE.
problem (which often is not attributable to the      Senior Program Manager
cooperative).                                        Cooperative Research ivetwork
                                                                              E x e c u t i v e Surnrnarv   -   xi




                                         EXECUTIVE SUMMARY
When an electricity consllmer has a problem            contains worksheets, eight in all, covering the
with an appliance-a light bulb that flickers, a        major categories of equipment-heaters,
television that "burns out," a motor that over-        motors, and electronics of various types. Each
heats, for example-a natural tendency is to            worksheet is a blueprint for a question-and-
complain to the electric utility. In actuality.        answer session with a customer, designed
many such problems are not the fault of the            to arrive at the cause of the customer's prob-
electric utility, and indeed may be beyond the         lem and a possible cure. By applying the sim-
control of the electric utility.                       ple theory in Part 1 and following the step-
    How does an electric cooperative, with limit-      by-step instructions, the representative should
ed customer-service resources, handle such             be able to diagnose many problems and
complaints? How can it efficiently separate prob-      decide whether intervention by the coopera-
lems that it can fix from [hose that are beyond        tive is warranted.
its control, and perhaps recommend cures or
preventive measures to consumers for the latter         The manual stresses a crucial fact: that prob-
problems? This manual suggests a way: It pro-        lems with equipment connected to both an elec-
vides worksheets for customer service represen-      tric power system and a communication sys-
tatives to guide them through a dialogue with a      tem-televisions with cable connections or per-
customer calling for help. By following the guid-    sonal computers with modem hookups, for
ance, a representative can ask the right ques-       example-can be caused by ezther system. Such
tions, get at the root of a problem, and then        problems are compounded when the two ser-
decide on an appropriate action: send a repair       vices enter at opposite ends of the building;
crew, tell the customer how to fix the problem,      physical separation of the entry point magnifies
or, for a problem that resists immediate solution,   the disturbances. Such disturbances should
call in an expert in the field.                      never be blindly attributed to "power line
    The manual is organized in two parts:            surges"; often the communication link can be at
                                                     fault, especially when it is improperly installed,
   Part 1reviews the nature of disturbances          as sometimes happens with cable connections.
   that can occur in the power supply to cus-            Scattered throughout Part 1 are short case his-
   tomers--disturbances such as voltage surges,      tories drawn from ordinary experiences-a
   lightning strokes, voltage swells, outages,       chandelier that inexplicably flickers, motor con-
   brownouts, voltage sags, noise, harmonics,        trollers that shut down when the electric utility
   unbalanced phases, and interaction between        adjusts its power factor. With such experiences
   the power system and a telephone or cable         and simple electrical theory as background, cus-
   TV system. A customer service representative      tomer service representatives should be able to
   can learn in this part how the disturbances       analyze many of the problems posed by distur-
   originate, how they affect electrical equip-      bances and find a solution for the consumer, or
   ment, and what can be done about them.            know when to call in expert help.
   Part 2 helps the customer service representa-
   tive troubleshoot over the telephone. It
                                                                                     D i s t u r b a n c e s a n d R e r n e d ~ e s- 1




               Disturbances and Remedies

               In Thls Section:Introduction; the nature of disturbances; too much voltage; not enough voltage;
               other power-line disturbances; system interactions



lnlroductlon   Many people believe that upsets or damage to          describes the possible interaction between the
               electrical equipment can be blamed on distur-         power system and a communications system,
               bances caused by the power distribution system        which is believed to be the cause of many Fail-
               or by lightning. However, such a belief is an         ures that are often misinterpreted as caused by a
               incorrect generalization; many times the problem      "power line surge."
               is in the equipment itself, not the power system.        The second part of the manual is formatted as
               This manual can help cooperatives' customer           a collection of worksheets that suggest interac-
               service representatives distinguish between           tions between the customer service representa-
               equipment-related and system-related problems,        tive and the customer reporting a problem.
               and either suggest a solution the customer or            An important fact is that upset or damage to
               alert the dispatcher that the cooperative's assis-    equipment that involves a communications sys-
               tance is needed. The manual presents in simple        tem can also be caused by disturbances on the
               terms the principles underlying unwanted upsets       communications system and should not blindly
               and damage and offers remedies for them.              be attributed to "power line surges." Ways to
                   This first part of the manual gives an            prevent this kind of upset or damage do exist,
               overview of the disturbances that can occur in        but some are beyond the control of the cus-
               the power supply to the customer. It briefly          tomer and the distributing utility. It is a matter of
               describes the origins of the disturbances and         recognizing the situation and selecting a techni-
               explains which disturbances are avoidable,            cally correct and cost-effective remedy. There
               which are unavoidable, whch are predictable,          may be cases where the risk or consequences of
               and which are entirely random occurrences. The        such damage or upset might be low, compared
               first part is organized in four sections. The first   to the cost of prevention. Therefore, the choice
               two are concerned with the most frequent but          of protecting or not protecting should be made
               brief disturbances-too much or not enough             thoughthlly, not left to neglect or ignorance.
               voltage (energy). The third section addresses         Armed with thls knowledge, customer service
                less frequent disturbances that are almost per-       representatives as well as customers will be         .
                manent, such as noise, harmonics, notches, and        guided toward a satisfactory resolution.
               voltage unbalance. The fourth and last section
2 - S e c t ~ o nO n e




The Nature of            Electric power is delivered to custonlers in the      second-engineers call that a 60-hertz (Hz) A  C
                         form of an alternating-current (AC) voltage that      voltage. This smooth waveform can be distorted
                         the utility strives to keep as constant as possible   under steady-state conditions, or have a tran-
                         (Figure 1.1).However, disturbances can and will       slent overvoltage or undervoltage.
                         occur in this voltage, in the form of either too         Some disturbances are brief-from millionths
                         much or not enough. In turn, the energy con-          of a second (microseconds) to thousandths of a
                         sumed by the load-what the utility sells-is           second (milliseconds). Other disturbances can
                         related to the voltage at which it is delivered.      be long, lasting from seconds to hours in the
                         The A voltage follows a sinusoidal pattern,
                               C                                               worst cases of service interruption.
                         with a complete cycle occurring 60 times per




                          FIGURE 1.1: Sine wave of an AC voltage supply.



Too Much                 Too much voltage can be the result of a normal          A third type of excessive voltage, a temporary
                         or abnormal utility operation, or the effect of an    oven/oltage, is not a part of normal operation,
Voltage                  external influence. Under normal operating con-       but is associated with a fault in the power sys-
                         ditions, the steady-state voltage is controlled by    tem. Temporary overvoltages can last a much
                         the utility withm a narrow band. Deviations from      longer time, and generally do not disappear
                         this band are rare, and the utility can readily       until the fault is cleared.
                         correct them, if informed of their occurrence, by
                         acting on voltage regulators and tap changers.        SURGES
                            On the other hand, there are momentary             Types and Origins of Surges
                         (transient) disturbances that occur under the         Surges have been blamed as the cause of equip-
                         typical operating conditions of a power system.       ment upsets or damage under many names:
                         There are two types of transient excessive volt-      power surges, spikes, glitches, impulses, and so
                         age that can occur under normal circumstances,        forth. In this report, the term surge is used, with
                         although by themselves they would be described        the understanding that it means events lasting
                         as "abnormal":                                        less than one cycle of the power frequency.
                                                                                  The two major causes of surges are
                            1. A surge is an overvoltage that can reach
                               thousands of volts, lasting less than one          Lightninean obvious and well recognized
                               cycle of the power frequency, that is, less        event (Figure 1.2)
                               than 16 milliseconds.                              Load switchinea type of event that includes
                            2. A swell is longer, up to a few seconds, but        major power system operations as well as
                               does not exceed about twice the normal             simple and seemingly benign switching by
                               line voltage.                                      the customer
                                                                                                    D i s t u r b a n c e s and R e m e d i e s   -   3




                                           Next to outages, surges are the         energy but can still produce upsets and even
                                           type of disturbance most fre-           damage in sensitive electronic circuits. The
                                           quently perceived by customers          severity of these surges depends mostly on dis-
                                           as the source of [heir problems,        tance. Nearby strikes are rare but may have
                                           and therefore merit a detailed          severe effects, distant strikes are more frequent
                                           examination.                            (increasing with the area of collection, that is,
                                                                                   with the square of the distance) but less severe.
                                           Lightning Surges. There are four        Again, these surges cannot be blamed on the
                                           types of lightning surges,              utility, but some customers might believe that
                                           described here in order of severi-      they came from the utility connection and
FIGURE 1.2: A surge induced by             ty. The first, rare but traumatic, is   attempt to place the responsibility on the utility.
lightning on an AC voltage.                a direct lightning stroke to the           The fourth and last type of lightning surge is
                                           building. Unless special protec-        one that actually arrives on the service drop of
                                           tion systems have been provided         the utility, as a result of a direct stroke to some
                         (lightning rods in plain language, air term~nals     in   element of the distribution system. A surge
                          protection jargon) with proper down-conductors           induced in the utility distribution circuits by a
                          and grounding, damage to the structure and               nearby stroke, just like the third type discussed
                          equipment can be substantial. Of course, such            above, can also appear at the service entrance. In
                          an event cannot be blamed on the utility. Few            contrast to the first three types, this fourth type is
                          residential customers go to the expense of               truly an excessive voltage delivered by the utility
                          installing a lightning protection system. Instead,       to customers. However, the general practice
                          they make an intuitive risk analysis: A typical          among utilities is to provide surge arresters on
                          lightning protection system can cost thousands           their systems, so that the residual surge that can
                          of dollars, while the probability of a direct            appear at a customer's service entrance is some-
                          stroke (outside of known areas of high lightning         what limited. The rare exception would be a
                          activity) is about once every 200 years for a             direct stroke to the pole or service drop, where
                          detached home.                                            the utility surge arrester would not intervene
                              The second type of lightning surge occurs             before a surge heads for the service entrance.
                          when a nearby stroke, and the resulting flow of
                          current in the earth, elevates the potential of the      Switching Surges. There are two types of
                          ground references of the building, including the         switching surges:
                          power system neutral that is bonded to ground
                          at the service entrance. This situation is called           Those that result from normal switching of a
                          ground potential rise. Meanwhile, the power                 load on or off by a customer or the utility
                          supply phase conductors, which are referred to              Those that are incidental to an intended oper-
                          ground through the secondary winding of the                 ation aimed at clearing a fault-a short circuit
                          distant distribution transformer (whose neutral is          or severe overload.
                          grounded there) remain essentially at the
                          ground potential of that distant transformer. A          Switching Surgesfrom Normal Operations.
                           large difference of potential can then occur            The first type of switching surge ("normal"
                           between the neutral and the phase conductors            surge) occurs whenever a load-any type of
                           at the service entrance of the building. That dif-      load-is being switched, either within the distrib-
                           ference of potential appears to be a surge deliv-       ution system or w i t h the customer's installation.
                           ered by the utility connection, but has nothing         Therefore, these can occur quite frequently.         ,

                           to d o with the utility operations.                     Those associated with the switching of a local
                              The third type of lightning surge is produced        load, especially if it is an inductive load such as
                           by the radiation of electromagnetic fields asso-        a motor, are generally short (a few microsec-
                           ciated with a lightning strike at some distance         onds) and d o not involve a large amount of
                           from the building. Such a surge involves low            energy. However, there is another source of
4   -   Section O n e




                        potentially large switching surges when capaci-        bank is switched on and off by a timer.
                        tor banks are switched for power-factor correc-        Capacitor switching surges from the utility have
                        tion. These can occur at random if the power-          been found troublesome in installations where
                        factor correction bank is controlled by the            the customer also has some power-factor correc-
                        instantaneous state of the system, or they can         tion capacitors: Magnification of the surges can
                        occur at fiied times in the day if the capacitor       occur. (See box, "Capacitor Switching Surges.")


                         Capacitor Switching Surges                             followed by an oscillating transient voltage
                         Capacitor banks have long been accepted as a           superimposed on the fundamental power fre-
                         necessary part of efficient electric power sys-        quency waveform. The peak voltage magnitude
                         tens. Switching capacitor banks on and off is          depends on the instantaneous system voltage
                         generally considered a norm1 operation for 3           at the instant of energization, and can rise to 2
                         utility system, and the transients associated          times the normal system voltage under worst-
                         with switching are generally not a problem for         case conditions.
                         utility equipment. The low-frequency transients,          Ordinarily, though, other components of the
                         however! can be magnified in a customer's              system help to keep the voltage rise to 1.2 to
                         facility (if the customer has !ow-voltage               1.8times the normal value, and the transient
                         power-factor correction capacitors) or result in       oscillates at frequencies from 300 to 1,000,000
                         the nuisance tripping of power-electronic              Hz.Figure 1.3 shows an example. recorded in
                         devices such as adjustable-speed drives.               the field, of a transient created by energizing a
                         Actually. capacitor energizing is just one of the      capacitor bank.
                         many switching events that can cause transients           Tsdnsient overvoItages caused by capacitor
                         on a utility system, but? because of their regu-       switching are generally not a problem for utili-
                         larity and impact on power system equipment.           ties because their peak magnitudes are usually
                         they quite oFten receive special attention.            just below the level at which surge protective
                            There are a number of transient-related con-        devices (SPDs) begin to operate. However,
                         cerns that are genemlly evaluated when distri-         these transients will often be coupled through
                         bution shunt capacitor banks
                         are applied to a power system.
                         However, these considerations
                         are related to the system design
                         rather than its operation, and
                         the customer has no control
                         over them. Remedies will essen-
                         tially be to learn how to live
                         with these unavoidable tran-
                         sients. When they originate from
                         the switching of a large capaci-
                         tor bank, it is unrealistic to
                         expect that the typical surge
                         suppressor has the energy-han-
                         ding capability to absorb them.
                          Characteristics of Energizing            -1.5 '       I        I                I        I
                                                                                                                            I   I
                          an Isolated Capacitor Bank.                   0      10       20       30     40         50    60     70
                          Energizing a capacitor bank                                        Time (milliseconds)
                                                                                                                        -


                          results in an inunediate drop in     IRE     1.3: ~ y p i c x o l t a g e a distribution bus during
                                                                                                  on
                          system voltage toward zero.          capacitor bank energizing.
                                                                             Disturbances and Remedies        -    5




 step-don-n tr.insfonners to c u , ~ x n eloails
                                          r                   The 5ize o f the utilit! 's 5n-itched capacitor
 (Figuse I.+). \vhere they can ~1ifec.t poner-                Ixunk is more thnn 10 times larger than t l ~ e
 quality-sensitive custonler ecluipment. i ~ r c h            c~~strxncr's customer h a i k .
 :IS cumputers.                                               The frequrnc! of the energizing oscillation
     If the customer uses c:ipacitors for the cor-            is close to the resonant freq~~enc!- theof
 rection of pon-er factor nn lhe lov-voltage                  circuit fol-med hk- the step-clorvn trans-
 side, higher transient or-ervoltages can rise                former and the customer's porver-hctor
 e\ en higher. This effect-"\ oltagr inagnifica-              correction capacitor Ixlnk.
 tion"+xcurs when a tmnsient oscillation. ini-                The customer's load has relatively little
 tiated by the energization of a urilih cqxacitor             resistance (this is t).pical of industrial p1:ltvs
 bank, excites a resonmt circuit in the l o w                 %-heremotors represent the major part of
 voltage system (the circuit is a combination of              the load).
 the inductance of the step-donn transformer
 and the capacitance of the customer's power-            Orclinarily. these transient switching or-en.olt-
  factor correction bnnk). The result is a higher        ages might simply clamage low-enern surge-
  oven-oltage at the lon-er voltage bus. The             protective devices or cause a nuisance trip of
  worst ~nagnification occurs w l ~ e n follon-ing
                                       the               power-electronic equipment. Nevertheless.
  conditions exist:                                      mcidents have been reported of complete
                                                         failure of end-user equipment.

I




 I                   5        10       15      20        25
                                                 Time (milliseconds)
                                                                     30       35

    FIGURE 1.4: Example of a customer's bus voltage during utility capacitor switching.
                                                                                        40        45        50




Switching Surges from Fault-Clearing. The sec-           voltage, and their duration ranges from hun-
ond type of switching surge, far less frequent,          dreds of microseconds to a few milliseconds.
occurs when a system fault is cleared, either by
the opening of a circuit breaker or the operation        Effect of Surges on Equipment
of a fuse. The latter can generate high surges if        Upset versus Damage. Surges impinging on
the fuse is located at the end of a long cable, in       equipment can cause upsets or permanent
which the fault current can store substantial            damage, with consequences ranging from barely
energy in the cable inductance.                          noticeable to total destruction or consequential
   The magnitude of these fault-clearing surges          damage.
can reach several times the normal system                   Among upsets, there are several possibilities:
6   -   Section One




                              Barely noticeable, with self-recovery: a click    have causecl damage to an appliance, it is
                              in a sound system or a flash on a video screen                                              1
                                                                                imposcant to determine if the appl~ance s a sin-
                              Pern~anent  and noticeable, requiring manual      gle-port or a multiple-post type.
                              reset: blinking clocks and VCRs                      Many appliances are still single-port equip-
                              Permanent but not readily noticeable:             ment, in spite of the trend to provicle sophisti-
                              data corruption                                   cated controls: a simple kitchen range is a
                                                                                single-port appliance, but a range controlled by
                              There are also several kinds of damage:
                                                                                a smart-house computer system is a two-port
                              Damaged components, repairable at a               appliance. A TV set with rabbit-ear antenna is a
                              service shop                                      single-port appliance, but the same set with a
                              Damaged components that are too costly            roof antenna or cable TV connection becomes a
                              to repair                                         two-port appliance.
                              Obvious and irreparable damage requiring
                              complete replacement of the equipment             Multiple-PortEquipment. More and more elec-
                              Damage such as internal equipment fire that       tronic equipment in homes and businesses
                              could set other objects afire                     requires a communications link, hence a com-
                                                                                munications port in addition to the usual power
                              Insurance statistics provide information on the   supply connection, the power port. Examples of
                           relative frequency of damage among insured           such two-port appliances include fax machines,
                           appliances. It is significant that video equipment   telephone answering machines, personal com-
                           is at the top of the list, and the discussion of     puters with modem or printer connections, and
                           multiple-port equipment damage under "System         cable-connected TV receivers and VCRs.
                           Interactions" at the end of Part 1 will explain         A possible problem is tknt although each of
                           why. A potit is a connection between a piece of      the power and communications systems may
                           equipment and the outside world. The line cord       include a scheme for protection against surges,
                           of an appliance is a powerpolst. The modular         the surge current flowing in the surged system
                           telephone jack on a fax machine, or the UHF          causes a shift in the voltage of its reference
                           connector at the back of a W set is a communi-       point while the other, nonsurged, system refer-
                           cationsport. In the modern home, both one-port       ence point remains unchanged. The difference
                           and multiple-porc appliances abound (Figure 1.51,    of voltage between the two reference points
                           and the same situation exists in commercial and      appears across the two ports. Depending on the
                           industrial installations. When the rime comes to     nature OF the appliance and its immunity, this
                           understand the origin of the surge suspected to      difference of voltage may have some upsetting
                                                                                or damaging consequences. The problem is so
                                                                                important that it is discussed in more detail in
                                                                                "System Interactions" at the end of Part 1.

                                                                                Remedies against Surges
                                                                                General Approach. At first glance, ~twould
                                                                                seem that if surges could be prevented from
                                                                                happening, many problems could be prevented.
                                                                                However, lightning cannot be eliminated. (There
                                                                                are some yet unproved schemes to dissipate the
                                                                                charges in a cloud and thus prevent lightning
                                                                                strokes.) Similarly, switching surges that occur in
                                                                                the utility system cannot be eliminated by the
    FIGURE 1.5: A lamp and a rabbi-ear N are examples of single-port            time they arrive at a customer's service entrance.
    appliances. A computer with a telephone modem connection is an example      Therefore, the general remedy is to install
                                             offers many examples of both
                                                                                (insert) surge-protective devices at one or more
                                                                                points of a customer's installation.
                                                                                              Disturbances and Remedies     -   7




                      Surge-ProtectiveDevices: What's in a Name?                Insert a TVSS for each sensitive appliance
                      The devices that can protect against surges are           (Figure 1.6)
                      called surge-protectiue cleuices, or SPDs, by engi-       Accept the offer (if made) fl-onl the utility to
                      neers, but that might sound too much like jar-            provide "whole-house protection" (Figure 1.7)
                      gon to most customers. The name that seems to
                      stick in the general public is surge suppressot:           Wholehouse protection consists of a protec-
                      which many manufacturers use for their trade            tive device at the service entrance complement-
                      designation, with a variety of catchy trade-            ed by TVSSs for sensitive appliances within the
                      marked names The Underwriters Laboratories              house. The service entrance protection is an
                      chose to call them transient uoltage sulge sup-         adapter inserted by the utility between the rev-
                      pressors (TVSSs), and that name or acronym              enue meter and its base. Variations exist, such as
                      generally appears next to the UL sign on the            a separate box connected to the meter base box.
                      product. In the utility industry, the generic name         With whole-house protection-that is, an
                      used in the transmission and distribution parts of      arrester at the service entrance and one or more
                      the system is surge arrester:                           TVSSs inside the building-the issue of .'cascade
                         Actually a surge cannot be suppressed nor            coordination" arises. The concern is that, if the
                      arrested; the correct word to describe what hap-        various protective devices are not selected with
                      pens is diverted. What these protective devices         due consideration, h e stress of incoming surges
                      do 1s simply divert a surge to ground, where it         may not be shared according to the capability of
                      can d o no harm. So a name that makes sense             each device. (See box, "Cascade Coordination.")
                      would be surge divertel*,but it was not picked          This is a concept that the residential customer
                      The consumer industry has settled on TVSS,              should not be expected to assess; it 1s the utili-
                      while the utilities stay with the long-used word        ty's responsibility to consider it and offer an
                      awester and use it for the more rugged devices          integrated, coordinated package of service
                      that a utility installs a1 the service entrance.        entrance protection and TVSSs.
                         The surge protection schemes for residential
                      customers are these:




FIGURE 1.6: A typical NSS with power and
telephone protection.                                     FIGURE 1.7: A meter-base arrester installed by the utility.
8 - Sectton One




                  Cascade Coordination
                  cisc:~ding s~lrge-protectiw    cle\-ice is :I con-     which millions of suppressors are in s e ~ ~ i c e
                  cept n.herehy two (or n~ose)     protectix e &\-ices   n-ith a relati\dy lo\\. clampin3 voltage. This
                  are connectecl :I[ tn-o (or 1nore1different            situarion will impose an upper limit to the
                  points of a pon-er sytem. The "upstrran~"              clamping voltqe of a candidate retrofitted
                  device (the one closest to h e utility's distribu-     arrester. Therefore. close attention must I x
                  tion system) is the first line o f defene: it is       paid to the selection of the relative clamping
                  designed to divert the IILIII< of an impinging         \-oltage of the devices. in \-ien-of the contlict-
                  surge. The "don-nstrealn" cle\.ices (those clos-       ing requirenlents for performance undrr surge
                  est to the equipment to be protected) are              conditions-a successful cascade-and reliabl?
                  intended 2s a final stage. cli\wting any remain-       n.ithstanding temporary power-frequency
                  ing surges, including those generateil within          oven.olrnges. Nevertheless. coordination still
                  the customer's wiring.                                 IIYJ!-   he possible if die arailable t~~cleoffs  are
                      Successful coordination of cascaded cle\.ices      understood. In the filrure. m-ell-informed users
                  is achieved when the hea\-v-du~-      upstream         coulcl avoid the pitfalls of poor coordination
                  device does indeed divert the bulk of the              01.the disappointment of implenlenting protec-
                  surge. instead of letting the don-nstream              tion schemes that cannot pro\-ide the hoped-
                  devices attempt to divert an excessive amo~int         for results.
                  of the surge current. In keeping n-it11 the ter-              .%I illusrmtion of [he effect of the relative
                  minology of this manual. the ~ipstseamcie7-ice         volrages and device separation on the enerR
                  n-ill be referred to as an armrer, while the            sharing bern;een two devices appears in
                  lighter duv. don-nstream devices n-ill be               Figlire 1.8. The fig~lre   shows 3 plot of the per-
                  referred to as s~lpprrssors.  The basic and criti-     centage of the total energy dissipated in the
                  CJI parameters for successful coordination of          suppressor, as a function of the distance sepa-
                  the arrester suppressor cascade include the            rxing the nvo devices. for \-arious cornbi~~a-
                  relative voltage clamping of the devices, their        tions of clamping voltages. In the plot. H. h1.
                  electrical separation through n-iring induc-           and L correspond respectively to a high (250
                  tance. and the actual waveform of the imping-          V). medium (150 V). and Ion- (130 V) voltage
                  ing surge                                              rating, in a 120-V rms circuit application. In
                      A w-ell-designedcascade arrangement maxi-          the designations H-H. H-M. H-L. etc., the first
                  mizes the benefit of surge protection n-ith a          letter is the rating of the arrester and the sec-
                  minimum expenditure of hard%-are.Another               ond letter is the rating of the suppressor.
                  benefit of a cascade is the diversion of large                Figure 1.9 shows an example of a coordi-
                  surge currents at the service entrmce. so that         mted scheme where the current in the sup-
                  they d o not flow in the building, and side             pressor is indeed small compared to the cur-
                  effects are thus avoided.                               rent in the arrester. This encouraging result
                      It is one thing to design a cascade based on        can sen.e as the basis for the selection of the
                  optimurn coordination where all the parame-             two devices in a schenle that a utility can offer
                  ters are under the control of the designer.             to its customers as an integrated package.
                  Such an opportunity exists in utiliy systems                  The active element in most surge protective
                   implemented under centralized engineering. It          devices is one or several disks of metal oxide
                  is an altogether different challenge to attempt,                                           the
                                                                         varistor (MOV) that perforn~ current diver-
                  after the fact, coordinating the operation of           sion function. The surge diversion capability of
                  surge-protective devices connected to the               arresters and suppressors increases with their
                   power system by diverse and uncoordinated              diameter. A typical cascade might consist of a
                  (and uninformed) users.                                 40-millimeter-diameter arrester and a 20-mil-
                      Promoting a coordinated approach may                linieter-diameter suppressor, described as a
                  come too late for the de facto sitiration in            40-mn1/20-mm cascade.
                                                                         Disturbances and Remedies          -    9




                                                                               h
                                                                 .-\itlios~~iie rcnlit! of Ixl\ ing nun)
                                                                 millions or 130-\ ok suppressors
                                                                 in~tdlcil 12o-\-oltsystelns makes ;I
                                                                              on
                                                                 \T ell-coorilinatetl casc:tde difficdt o r

                                                                                            at
                                                                 puhaps ~un;~itninalAc. least in the
                                                                 nr;u future. n cooperative can still
                                                                 take cemin steps lo i~npro\.e       coorcli-
                                                                 nation in a protection sr-stem. .is a
                                                                 compromise. :I cascade n ~ t h     equ:il
                                                                 \ oltage ntings 6 s the arrester and the

                                                                 suppressor can offer successfi~lcoor-
                                                                  clinution. if the impinging ssurges :Ire
                                                                  rel:~ti\.elyshort. The coordination of :I
                                                                  simple cascade of an arrester and :I
                                                                  s u p p x s o r of equal voltage rating.
                                                                  hoth connected line-to-neutral. 1s
                                                                  slightly improwd b!- the larger diame-
                                                                  ter of the arrester. Mon-el-er.an unfd-
                              Distance between arrester           voralAe ccimhinxtion of rt~lerances      for
                               and suppressor (meters)            the two devices c a n wipe out the
FIGURE 1.8: Relative energy deposited in the suppressor           impro\.ement-for example, if the
by a typical high-energy surge for various combinations           arresrer clamping voltage is at the
of 250-volt (H), 150-volt (M), and 130-volt (1)ratings, as        upper end of the tolennce band and
a function of separation distance.                                the suppressor is at the Ion-er end of
                                                                  the tolerance band. effecti\.ely making
                                                                  the suppressor t l ~ r  lower device
                                                                  hence the one that mill have to divest
                                                                  Inoa of the surge.




        -1 000
                 0       10        20      30      40      50      60      70        80       90      100
                                                   Time (microseconds)
                     -   -


    FIGURE 1.9: Division of surge current in a cascade of two 150-volt devices: I , is the current
    in a 40-mm-diameter arrester and I, is the current in a 20-mm-diameter suppressor, with
    10-meter separation for the same 3000-ampere surge as in Figure 1.8.
10   -   S e c t i o n One




                                In large business or industrial installations       of variable-speed drives (these are beginning to
                             with internal feeders, suhpanels, and fairly long      appear in residenrial heating and air-condition-
                             branch circuits, the question of cascade coorcii-      ing systems) might experience a trip-out during
                             nation is more complex than for a simple resi-         a swell. That possibility raises the question of
                             dence. It should be assessed by the specialist         ability to withstand swells, to be taken up with
                             responsible for the electrical installation.           the vendor of the variable-speed drive.
                                                                                       There is no device that can suppress a swell
                             SWELLS                                                 the way a suppressor "suppresses" a surge; the
                             Origins of Swells                                      remedy must be inherent immunity of the
                             The disturbance called a swell is a brief increase     equipment. Thus, there is little that the user-
                             in the line voltage, typically less than 20 or 30%,    residential or industrial-can do short of
                             associated with load rejections and sluggish           requesting the vendor to provide appropriate
                             voltage regulation response. The AC voltage            designs for the equipment.
                             sine wave remains essentially undistorted, but ~ t s
                             amplitude is increased for a few cycles or a few       TEMPORARY OVERVOLTAGES
                             seconds (Figure 1.10).                                 Types and Origins of Temporary Overvoltages
                                                                                    Temporary overvoltages are abnormal distur-
                                                                                    bances, at the power frequency, that occur
                                                                                    under the usual (normal or abnormal) operating
                                                                                    conditions of a distribution system. The princi-
                                                                                    pal causes are system faults over which the utili-
                                                                                    ty has little or no control (animals, storms, vehi-
                                                                                    cle collisions) and a troublesome situation of a
                                                                                    lost (open) neutral connection in the service
                                                                                    drop to customers, in particular the residential
                                                                                    120/240-V three-wire systems.

FIGURE 1.10: A voltage swell lasting eight cycies.
                                                                           I        Distribution System Faults. Overvoltages on the
                                                                                    distribution system originate from a variety of
                                                                                    system faults such as line-to-ground insulation
                             Effect of Swells on Equipment                          failure within the distribution transformer.
                             Swells lasting only a few cycles are unlikely to       Overvoltages caused by system faults can reach
                             cause any damage, and only the most sensitive          2.5 times the normal voltage. Depending on the
                             electronic equipment might experience a                settings of the protective schemes, it can take as
                             momentary disturbance. On the other hand,              long as 5 seconds to clear the circuits.
                             swells lasting more than a few cycles can cause           A rare but possible system fault occurs when
                             a trip-out of protective circuitry in some power-      the same pole carries two systems at different
                             electronic systems. Variable-frequency drives          voltages and a collision, high wind, or ice causes
                             (also called adjustable-speed drives) often            one set OF conductors to fall onto the other. This
                             include an overvoltage sensor in their electronic      scenario will produce overvoltages proportional
                             control, which can cause a trip of the system,         to the difference of the two system voltages.
                             with or without restart. The safety issue of auto-
                             matic restart versus mandated manual-only              Open Neutral. An open neutral situation can
                             restart is well known among plant engineers.           occur as a result of corrosion in underground
                                                                                    service drops, falling branches or ice on
                             Remedies against Swells                                three-conductor overhead service drops, and
                             For the residential consumer, there is no con-         even a loose connection of the neutral in a ser-
                             cern about damage and only a small likelihood          vice panel. Service drops with aluminum neutral
                             of some upset of an electronic appliance. A user       conductors are more prone to this type of fault.
                                                                                    Disturbances and Remedies             -   11




Utility engineers can report many anecdotes                        sides of the 120/240-V custonier installation are
about that type of disturbance.                                                                  the
                                                                   not balanced. the side w ~ t h lightest load
  As the box "When a Neutral Opens" explains,                      experiences a large increase from 120 V, theoret-
what happens is that if the loads on the two                       ically almost up to the full 240 V


 When a Neutral Opens                                               (see Figure 1.11). l ' h e on[! remaining connei,-
 Open neutral connection. in 120 1-to-\. CLI.;-                     tion is the r \ \ c lines. Ll :ind 1.1. x.ross \\ hic.11
                                                                                                        -
 t0111er i l l d t ; i ~ [ : ~ t i O lcan occur under wwral cir-
                                      l~                            the full 2tO-\- supply is niaintainccl.
 cumstance.;. including:                                                '[he putenlial xt the midpoint Iwt\veen thc
                                                                    tn-o Ioatls %, :mil Z2 \\-ill be w ~ ~ i e \ \ ~ I ~ e r e
     W~en     corrosion of ;un aluminum under-                      i>et\\-em1 potential o i LI kind L1, in in\-ersc.
                                                                                thc
     ground s c n k e re~cheb acute Stag!
                                      an                            proportion to thc \-alucs o i Zl mil Z2. If, for
     \Yhen the neutral n k e of n .;cparLlre-c.cx-                                             IOU
                                                                    instance. Z2 i \ r n ~ ~ c h el- than TI. a ' l l SS
     ductor senicc drop is brnlien h!- Giling                       connectecl on the L1 side \\-ill experience a
     hranches or icing                                              se\.ere o\.en oltagt. (as \xi11 the equip~nent       rep-
     \Yl~enan intermittent loow connection                                          Z
                                                                    resented I>). I , Hone\-er. ~ h i l e    mosL equip-
     exists in the service n:~nel                                   men1 h:is some toieranc'e h r 3 moilemre o \ w -
                                                                               .
                                                                    \ c k ~ g eTYShs. in prticul;i~-  those that claim
 (Note that all of the : ~ h o \ e .'\\-lien"C ~ ~ I L I S - inn clamping \ ollnge. are quite wnsitil-e to that
                                       are
 es-not "if and n.hen"-hecause ;dl of these                                                        is
                                                                    condition. Tlii:. sir~ution prol,.,il>l!. the cause
 c i r c u ~ ~ ~ s t a n c es o m c n h ~ likel!. ro occur :it
                       are ~              t                         of most reported catastrophic Failures o T\-SSs.
                                                                                                                   f
 some point: it is onl!- a marlel- of pldxlxlir!                                                on
                                                                         Some p~~ldications powt.1- qualit!- include
 and frequency of nccurl-ence.1                                     an illustration of n scren driver (presumalAy
     In 0-pica1 installations. the t\\o hal\.es of                   intended to tighten loose connections i n-it11 3
 the pon-er suppl!.. o n e ~ c h        side of rlie center-        caption that reads -'the most useful power-
 tap neutral connecrion, are d c i o m exactl!-                     qiuali~tool"!
 I~alanceci.    and
 sometimes are
 highly unbalanced.                                            Line
 If the insral1:lrion
 neutl-al beconics
 clisconnectecl from
 the utilih. neutral.
                                     240,        Neutral1
                                                  pund  yX                                                            voltages
 voltages          and I >
 appear o n each                                          I ~v   O          neutral                            v2


 side of the non--
                                                               Line
 disconnected
 inst:tllation I I C L ~ X I        FIGURE 1.1 1: Unequal line voltages caused by an open neutral.



Effects of Temporary Overvoltages on Equipment                     voltage reduction o n the secondary. Distribution
Overvoltages, whether a result of distribution                     arresters are generally selected for their ability to
system faults or open neutrals, can be quite                       survive temporary overvoltages. However, many                   .
destructive for equipment if allowed to last more                  consumer-type n S S s are likely to fail during a
than a few cycles ( ~ n
                      which case they might fall                   temporary overvoltage [see box, "Lower Is Not
in the category of swells). Power equipment is                     (Necessarily) Better"]. In Fact, the major cause of
designed to survive these overvoltages: trans-                     TVSS failures is a temporary overvoltage, rather
formers are likely to saturate, providing some                     than an unusually large surge.
12   -   S e c t i o n One




                              Lower Is Not (Necessarily) Better!                  tiown\~ard,,auction' among mnnufacrurers
                              The funclanienral purpose of a surgc-protectlw      who xwnced to be in the 330-V categor?.
                              device is to reduce tlie stress imposed on load     overlooking the undesirable side effects of
                              equipment n k n surges occur on the : C   \         such a tight clamping.
                              power system. Surge protective de\.ices (SPDs)          Actually. most load equipment is more
                              do this by di~wting current o an imping-
                                                    the          f                robust to surges than Tb5S manufacturers
                              ing surge to gro~ind  through a low impedance.      imply by offering these low clanlping \.olrages.
                              The effect is a subsrantial reduction of the        For instance, a 500-V clamping voltage would
                              impinging voltage surge.                            be quite adequate for protecting equipment.
                                 . SPD is a volrage divider in n-hich the
                                 b                                                Furthermore-the point of the axiom ,'Lower is
                              vo1t;lge on its low side (the side connected t o    not better!"-a n;SS clamping at 500 V would
                              the load) becomes lower as the surge current        nor respond to most swells or temporary over-
                              increases. "cla~nping" ~olrage
                                                      the         ilnpressed on   voltages, a characteristic that is highly desir-
                              the load.                                           able. Such a passix.e sinration would help in
                                 Before the proliferation of SPDs. made pos-      retarding the aging process of MO\'s. More
                              sible by the development of metal-oxide varis-      important, it certainly would reduce the inci-
                              tors (MOVs). the perception existed that the        dence of the catastrophic failures that are peri-
                              threat of surges was the voltage they can           odically reported in trade magazines.
                              develop at the terminals of a load. Thus.               Some manufacturers have responded to the
                              people thought that clamping that voltage           argument by offering guarantees or no-ques-
                              to a Ion- lexd was desirable and, intuitixdy        tions-asked replacement. Nevertheless, failure
                              but erroneously. the lower the better. This         of a WSS from a temporary ovenoltage might
                              perception was reinforced by the decision of        still be a traumatic experience for a homeown-
                              the Underwriters Laboratories to require man-       er. Those few manufacturers who subscribe
                              ufacturers of TVSSs (UL Standard 1449) to           to the "Lower is not better" philosophy should
                              show tlie clamping voltage of their product         be rewarded by being chosen when con-
                              on the package. picking fi-om a List of discrete    sumers go through the q u a n d a ~ @.ing to
                                                                                                                       of
                              steps starting with 330 V for 120-V applica-        select from the multitude of WSSs offered on
                              tions. This UL requirement triggered a              the shelves.


                             Remedies against Temporary Overvoltages              diversion are limited. In contrast, a temporary
                             The nature of temporary overvoltages makes it        overvoltage involves the full power of the sys-
                             difficult if not impossible to prevent them, and     tem, and no device can absorb that level of
                             therefore they must be accepted as a probable,       energy. As noted above, some equipment can
                             but hopefully rare, event. Surges can be diverted    be designed to withstand the overvoltages, but
                             because the energy levels to be absorbed in the      that decision is beyond the control of a utility.



Not Enough                   OUTAGES                                                 Outages rarely damage equipment directly.
Voltage                      Outages represent the worst type of disturbance      Indirectly, of course, industrial processing equip-
                             for the operations of a customer. They can have      ment (for metals, plastics, textiles, semiconductor
                             a duration as short as a few cycles, the typical     devices, and so forth) shut down by an
                             situation when the breaker of a feeder trips out     unscheduled outage can suffer damage. The
                             on a fault and the fault is cleared, with automat-   material under process is not only mined but
                             ic reclosing (Figure 1.12). Other outages can be     can also jam the equipment, with painful and
                             much longer, as when the distribution equip-         time-consuming cleanup operations.
                             ment suffers a major fault (downed lines, cata-         Less dramatic consequences or cessation of
                             strophic failure of transformers or switchgear).     operation can range from inconvenience to loss
                                                                                              Disturbances and Remedies      -   13




                                                                               operational cost of an outage justifies the invest-
                                                                               ment in a dual feeder system. Pessimists have
                                                                               noted, however, that when an installation
                                                                               depends on two feeders, it might be subjected
                                                                               to twice as many sags because each feeder car-
                                                                                                of
                                                                               ries a likel~hood sags.

                                                                               SAGS
                                                                               Power quality engineers call "sag" an event
                                                                               when the line voltage is reduced for a few
                                                                               cycles to a level of less than 80% of the normal
                                                                               voltage (Figure 1.13). This type of disturbance
                                                                               can trigger upset or shutdown of control circuits.
                                                                               Sags rarely cause equipment damage but are the
                                                                               cause of many complaints of malfunction.
FIGURE 1.12: A very brief outage (top) and a very long outage (bottom).
                                                                                  Sags have their source in faults in a feeder that
                                                                               cause a large current to be drawn in the feeder,
                         of revenue. Individual consumers also can suffer      hence a voltage drop in the bus from which
                         from loss of power needed for heating, air con-       other feeders draw power. Many power quality
                         ditioning, and food refrigeration. One utility,       engineers consider sags as the major cause of
                         with a mixture of seriousness and facetiousness,      equipment malfunctions-but rarely, if at all, of
                         used to describe the severity of outages by the       damage. Upsets affect primarily the information
                         number of claims filed for spoiled freezer loads      technology equipment. Also affected are simple
                         of frozen raspberries!                                power devices controlled by a magnetic motor
                             The obvious remedy against outages at the         starter, which can drop out and stop a process.
                         customer level is to provide a standby source of         Field studies of sag-related disturbances in pro-
                         power, either a storage battery or an engine-         cessing equipment have revealed that the source
                         generator set. The battery-power approach, gen-       of the problem can be a simple relay in the con-
                         erally called an unintemptiblepower supply            trol system, rather than a major disturbance in the
                         (UPS), is a very popular remedy. It is applied at     power equipment. In such cases, a very effective
                         all power levels, from the small package favored      remedy is to provide the control system with a
                         by reliability-conscious computer users, to a         UPS, or even with a simple constant-voltage
                         building-wide system where loads are segregat-        transformer that can ride through most sags.
                         ed into essential and nonessential. There are
                         various types of UPS offered by manufacturers          BROWNOUTS
                          in a highly competitive market, each with per-        In periods of hlgh demand where the system
                          formance characteristics aimed at minimizing or       capacity is reached and would be exceeded, util-
                          avoiding altogether the momentary disturbance         ities reson to the scheme of deliberately reducing
                         when power is transferred from the utility to the      the voltage by a few percent. The effect is a
                          standby source.
                             For large industrial
                          loads, schemes of dual
                          feeders with an automatic
                          transfer switch have been
                          applied successfully by
                          mutual agreement
                          between the customer
                          and the utility. Such an
                                                            FIGURE 1.13: A sag lasting 10 cycles with the line voltage reduced to
                          approach is justified
                                                            55% of normal.
                          when the financial and
14   -   S e c t o n One




                                                                by
                           reduction of the power consun~ed most loads,           curve, n ell known to power-quality speclalists
                           with some exceptions in the case of process con-       as the CBfibk4 curve, has recently been updated
                           trols that include a voltage regulating scheme         ancl IS now called the Z77C cwve (for the
                           that defeats the objectwe of the brownout.             Inforniatlon Technology Industry Council). See
                                                                                  box. 'The CBMA Curve."
                           SUSTAINED UNDERVOLTAGES
                           A very severe brownout might cause overheat-           FLICKER
                           ing of compressor motors, and some people              When light sources (mostly incandescent but
                           believe that domestic refrigerators therefore          also some fluorescent) are supplied from a
                           should be disconnected when the lights are very        power line in which repetitive sags occur, a
                           dim. This perception needs clarification, and util-    flickering effect is produced that h~unansfind
                           ity engineers should quantfy the risks involved.       annoying. The correct term to describe the
                              Another damaging consequence might be the
                           failure of some electronic voltage regulators built
                           into computer-based equipment (generically               The Case of the Flickering Chandelier
                           called "information technology" equipment).              In one nnecclote. a customer comphined o f
                           Such equipment has an intermediate regulating            tlickering lights to the electric utilit!-. \\ liich
                           stage that can become overloaded and overheat            installed a strip-cl~itr~recortlcr :kt 111c sen ice
                           when attempting to compensate for the voltage            entrance in response (:IS if that coulcl cletecr
                           reduction. Anecdotes have been circulated, and                                  Of
                                                                                    small tli~crualions!). course. none \yere
                           the phenomenon has been demonstrated in the              cletected. It turned our 111x1the customer l~atl
                           laboratory, but is confined to isolated cases. It        left an enipt!. electric skillet o n \vhile suppel-
                           is recounted here as a yet another hint that             n.ns k i n g enjoyed in the dining room. 111
                           equipment failures should not blindly be attrib-         that \.int:tge-era house. the sliillet ( 1500 n atrs
                           uted to surges.                                          on a =l-+.\KG wire) nnd the chandelier
                                                                                    n-ere on the same Ixtnch circwit. The flicker
                           CHARACTERISTIC CURVES                                    n-as cnusrtl h. the thermostat of the skillet
                                                                                                   !
                           The information technology industry has devel-           cycling o n and off. Flickering cmdles on the
                           oped a characteristic curve describing the toler-        dining room tahle ma\. be ro~ixintic. :I    hut
                           ance of equipment to undervoltages (mostly               flickering chandelier is declared :innoying.
                           sags) and overvoltages (mostly surges). That


 The CBMA Curve                                                      equipinent could stand. It was not rhoroughly tested or vet-
 111the 1:lre 19'0s. computer mnnuf;~cti~rers usersand               ifiecl zit t1i:lt time. Although the ponw-supply ~echnologies
 reached a consensus on the pawn quality (use of the term            of husiness equipment have improwcl. some m:tnuf~~cturers
                      d)
 had just s t a ~ ~ ethat woulcl he necess:u.)- to ensure ~indis-    :[re still reluctant to incorporate them into thcir procli~cts
 turbecl operation of computers. The concept-as a design             hecause o f competitive market constlxints.
 god. not a specification-\~:ts first proposed as relev:~ntto             In the 1990s. incrr:ising intcrcst in solving p o n w quality
 mainfi:~me compurers and presented in the form of a cloii-          prohlems led to c.xtensive resr:trcli in thc tole~ince f vari-
                                                                                                                                  o
 hle cun.e showing a l o ~ w limit : I I ~an upper limit for
                                   r                                 ous cclurpment to power supply clisturlxmcrs, in particular
 acceprahle mains \.oltage. or. in other n-orcls. the clesi~.ahlr    .;;igs. Changing technolog!- in computer equipment-non.
                              n
 rolel.ance of e q ~ ~ i p m etot p o n w supply rariations. This    classified as infomiation technology equiplnent (ITE) also
 ~ I X I I T became known :IS the CBEALI curve and n-:ISsoon         led ro >I revision of the lin~its,  anel :I re\-ised curie x i s
 consiclererl-perhaps nor an appropriate extension-as                issued in 1996 17). the Information Technology I n c l i ~ s t ~ ~
 ,~pplicahle some eleclronic equipment other than com-
                 to                                                  Council IITIC). together with an qq>lication note (Figure
 puters. ancl n.as cited in sever:ll stand:ircls. The origin:ll       I . 14).
 cun.e nxs a ch:tlIenging consensus-building effort. It was               Cpdxez to this information may he found ;tt the x'eh sire
 :I committee agreement on what people thoi~ght           the                                     itic
                                                                     http: w-~\~.chenla.org sire-map inclcs.lltml
                                                                                                                                                Disturbances and Remedies       -   15




                                                                                                                                 behavior of the power supply is uoltngejltictun-
                                                                                                                                 tioiz, but jlickeriizg is often used to describe the
                                                                                                                                 quality of the power, even though it is only the
                                                                                                                                 effect, not the cause.
                                                                                                                                    Voltage fluctuations can be considered repeti-
                                                                                                                                 tive sags OF low amplitude (the human eye can
                                                                                                                                 detect light output variations caused by a frac-
                                                                                                                                 tion of a percent fluctuation in the voltage,
                                                                                                                                 when the fluctuations occur at rates ranging
                                                                                                                                 from a few seconds to about 20 per second).
                                                                                                                                 Typical sources are arc furnaces (not too many
                                                                                                                                 around) and welding machines (arc and resis-
              breakdown concern
                                                                                                                                 tance spot welding).
                                                                                                   106%                             There is no remedy that the customer can
   100%                                                                                                                          apply when the fluctuations come from an inter-
                           tolerance envelope

                                          -
                                                                                                                                 mittent load of a neighbor. (Be sure that the skil-
              Lack of stored energy ~n                                                                                           let or flat-iron is not on!) If the complaint sounds
              some manufactures'                                                                                                 serious, the only remedy is for the utility to
              equipment                               . 30%'
                                                                                                                                 investigate where the intermittent load is, and
                                      I                             I    1    I            I                        I
    096000~         obi           01              0510              610       30         1001                     1000           negotiate a solution with the offender. Power
                                          Time in cycles (60 Hz)                          seconds                                quality specialists are acquainted with a variety of
    500                -       -----                                                                                             solutions, but each is to be applied case by case.

                                                                                               1




    120
            Voltage tolerance
                                                      L --*                                        -          + - I -1
          - envelope
    O
    '     .                                                         t-
                                                                     -                             -        -r I

                 "&        '   'it,           i
                                            lms3ms
                                                  '   I'       dI
                                                                Mrns
                                                                        ""%   '    ' I &
                                                                                   05s
                                                                                               '       .'i'doo'
                                                                                                             10 s
                                                                                                                        doc
                                                                                                                         Stear
                                          Two scales on horizontal axis:
                                          1. Duration in cycles
                                          2. Elapsed time

FIGURE 1.14: The original CBEMA curve (top) and the updated lTlC
curve (bottom).
1 6 - Section One




Other
-   -
                        Other disturbances, less frequent than the "too        Impedance is not constant or because they draw
                        much" and "not enough" lust described, can also        currents that are not proportional to their
Powelcline              occur as the result of the operation of the distrl-    impedance. This type of load is becoming more
Disturbances            bution system and interactions wlth customel           widespread as consumer electronics proliferate
                                       disturbances include noise, har-
                        loads. ~ h e s e                                       and as new-, sophisticated power-control
                        monics, notches, unbalance, and carrier signals.       schemes aimed at improving efficiency are built
                                                                               into some major appliances. The presence of
                        NOISE                                                  large harmonics is readily visible in the voltage
                        The term noise is loosely used to describe small       waveform. Small, but potentially objectionable,
                        disturbances (a few volts at most) at high fre-        harmonics require a more sophisticated instni-
                        quencies (note the plural). See Figure 1 15. The       ment, such as a power-quality monitor, to detect
                        sources of noise include chattering relays (a          and quantlfy them.
                        short-duration event) and coupling of radio fre-
                        quencies from a nearby broadcast antenna (a            Effect of Harmonics on Equipment
                        quasi-permanent situation).                            As a result of the increase in occurrence of har-
                                                                               monics, the subject has become a hot topic (pun
                                                                               intended) because the effect on equipment can
                                                                               be severe overheating. The problem starts
                                                                               because nonlinear customer loads generate cur-
                                                                               rents at harmon~c   frequencies. (In the jargon of
                                                                               the applicable standards, this is called harmonic
                                                                                    &   .




                                                                               emission.) There are several undesirable results
                                                                               from this situation:

 FIGURE 1.15: Noise superimposed on an AC voltage.                                1. Effective (root mean square, or RiiS) cur-
                                                                                     rents in conductors are increased, in par-
                                                                                    ticular in the neutral of three-phase sys-
                           In keeping with Federal Communications
                                                                                    tems. These increased currents can cause
                        Commission (FCC) requirements, most domestic
                                                                                    overheating because the wiring installa-
                        equipment has a filter in the power cord that
                                                                                    tion, done in accordance with earlier ver-
                        limits the emission of high frequencies back
                                                                                    sions of the National Electrical Code
                        into the power cord. Industrial equipment has
                                                                                    (NECm,trademark of the National Fire
                        similar FCC requirements, but less stringent. By
                                                                                    Protection Association), made no provi-
                        reciprocity, this filter also limits the penetration
                                                                                    sion for that situation.
                        of line-conducted noise into equipment; this
                                                                                 2. The harmonic currents clrculate in the
                        fact is worth keeping in mind when considering
                                                                                    deltz-connected secondary of wye-delta
                        the purchase of a TVSS making claims of
                                                                                    transformers but not in the primary side,
                        adding noise filtering to its prime mission of
                                                                                    therefore primary overcurrent protection
                        surge protection.
                                                                                    is not effective and the secondary can be
                                                                                    severely overheated.
                        HARMONICS
                        Harmonics are currents
                        and voltages at frequen-
                        cies that are multiples of
                        the fundamental 60-Hz
                        waveform (Figure 1.16).
                        They are the result of
                        normal operation of cer-
                        tain loads, called non-
                        linear because their
                                                          FIGURE 1.l6:An AC voltage distorted by harmonics.
                                                                      Disturbances and Remed~es 17
                                                                                              -




  3. If the harmonic currents are not filtered         include the providing filters as a retrofit option.
      out or canceled at the point of common           As of 2001, the issues are still the subject of
      coupling (as they are in 2 above), the           much debate, and should be reviewed by
      currents flow in the utility distribution sys-   power-quality specialists before expensive
      tem and cause a voltage distortion in the        and possibly counterproductive measures
      supply of adjacent loads, proportional to        are implemented.
      the current and the utility system imped-
      ance. In other words, systems with rela-         NOTCHES
      tively low available short circuit capacity      "Notches" can be created in the supply voltage
      will experience more voltage distortion          when large power-electronic drives in adjacent
      for a given nonlinear load than systems          loads cause a momentary short circuit between
      with high capacity.                              the phases that power the drive, each in turn.
                                                       These are called commz~tation    notches and occa-
Remedies against Harmonics                             sionally cause some interference with other
Remedies against harmonics are essentially com-        loads that use the 60-Hz power frequency as a
promises in a range of extremes. One such com-         controlling signal (Figure 1.17).
promise is to control harmonic emission by                In a sense, notches may be considered as a
mandating limits for each and every piece of           special case of harmonic emission, and the
equipment, the approach presently taken by             remedies, if interference is noted, are similar to
some European countries. Another approach,             those mentioned for harmonics in general.
which has gained accep-
tance in the United States,
is a voluntary compromise
where limits for harmonic
                                                    '      ,           '    ,
emissions at the point of
common coupling are
only recommended.
    Consumers have practi-
cally no control over the
harmonics that their                FIGURE 1.17: Commutation notches on an AC voltage.
equipment can generate,
but the perception in the
United States is that, for the moment, they do
not pose problems. This laissez-faire attitude        UNBALANCE
mlght change if harmonic-generating loads such        Voltage unbalance between phases occurs when
as electronic ballasts and variable frequency dri-    a three-phase system supplies single-phase loads
ves for heating and air conditioning were to          that draw unequal currents. Three-phase loads
become a larger portion of the total consumer         supplied under those conditions can be adverse-
load.                                                 ly affected, with overheating of motors in partic-
    In commercial and office buildings with older     ular as a symptom. Variable-frequency drive sys-
wiring and a large amount of information tech-        tems have a tendency to magnify the problem
nology equipment, supplied single-phase from a        by skipping some OF the six half-cycles that are
three-phase system with shared neutral, harmon-       expected, each in turn, to deliver power to the
 ics can cause overheating problems. Later ver-       drive. Thus, a severe current unbalance can            ,
 sions of the NEC recognized the problem and          result from a moderate voltage unbalance.
 have mandated larger ampacity For shared-neu-           The remedy for this situation is under the
 tral conductors.                                     control of the end user and is simply to reassess
    Industrial customers are more concerned           the allocation of single-phase loads from the
 about harmonics because some of their loads          three-phase system.
 can have a significant emission. Remedies
18 - Section One




                   CARRIER SIGNALS                                           These are isolated cases for which case-by-
                   Occurrences of interference fro111carrier                 case remedies have been developed by power-
                   signals have been described in anecdotes.                 quality specialists.



System             THE PROBLEM                                               power supply. Furthermore, the problem can
                   A special kind of surge problem is that of an
Interactions       interaction between the power system and a
                                                                             arise even if both of the systems have been pro-
                                                                             vided with surge protection, leaving a customer
                   communications system, as briefly mentioned in            thus afflicted puzzled or disappointed. The effect
                   the beginning section of this part, "Surges." This        of this interaction is to shift the reference poten-
                   case merits special attention because it can be           tials of the two ports during a surge, as explained
                   misinterpreted as being caused by the utility             in the box *'ShiftingReference Potentials."


                     Shifting Reference Potentials                             pip-n-l~icli can be espected in residenlial
                     To illustsate the problem of shifting reference          n.iring-a large loop is formed. embracing the
                     potentials. a lal>orato~)- replica of a residential      fl~lx produced by the surge current in the cop-
                     wiring system xvas used to malie nleas~11-e-             per pipe.
                     ments during surge events produced hy inject-                  Figure I 19 s11on.s the recording olh~ainecl
                     ing a surge into the wiring. In Figure 1.18. 11          in the laboratory replica of residential wiring.
                     modern-equipped PC is connected 11). its                 For a rate of change in the surge current of -5
                     pon-er porr to a lhranch circuit. and by ~ t s           .A )IS (amperes per microaeconcl). typical of
                     tnocleni port to the telephone service of the            standard test wiveforms a peak of i . 3 k\. is
                     house. For a worst-case scenario. the power              induced in the loop and appears betn-een the
                     ancl telephone s e ~ ~ i c enter the house at
                                                es                            m'o ports.
                     opposite ends.                                                 . relatively simple retrofit solution is to
                                                                                     \
                        .inopen loop is formed by the copper pipe                       the
                                                                              cq~lalize difference of voltage bemeen the
                     or ground concluctor used as a bonding cotl-             two systems by 3 device designed for the pus-
                    d~ictor. eq~~ipment
                              the             grouncling concluctor of        pose and inserted in both communications ancl
                    the branch circuit feeding the PC. and the tele-          pon-er links j~lsrbefore they enter [he nppli-
                     phone wires from the netn ork interhce device            ance. This device, defined in IEEE Standard
                    (KID) to rhe PC. If a surge impinges on the               1100-1992 as a "surge reference equalizer." is
                    external telephone plant. it is
                    diverted by the TID via the
                    copper pipe to the cornmon
                    grounding point of the house.
                    :1t the poxer senice entrance.
                    The surge current in the cop-
                    per pipe creates a changing
                    magnetic tlus around the pipe.                                                                         device
                    which induces a voltage in the                                  yCold water ppe
                    loop. This voltage xvill appear
                    benveen the m-o I'C posts if
                    they are separated by a high
                    impetlance (of unknon-n surge                                                               -
                                                                                                                -

                    volrage withstand capacity).                FIGURE 1.18: Power and telephone services enter the house
                    Wth the telephone wires rout-              a t opposite ends. A personal computer is connected across
                    ed avay from the copper                    the two systems.
                                                                              0

                                                                              05

                                                                              OOL   g
                                                                                    0
                                                                                    E
                                                                              OSL 8

                                                                              ooz




     OZ       81      91     PI      ZL    01          8        9
         I                                                                    0
               loimpuoa an!i3alold
                                                                                    3
                                                                                    P
                 pue uod auoqdalai                                            002
                   uaawaq afieilon = A                              A
                                               x e u I\ 00z f
                                                                              OOP




                                                                        ~oi3npu03an!i>aio~d
                                                                         pue uod auoqdaja]
                                                                           uaamiaq afieilon =A




61   -   salpaluau pue s a 3 u e q ~ n i s a
                                                                                                     D ~ s t u r b a n c e sa n d R e m e d e s   -   21




                         REMEDIES AGAINST SYSTEM INTERACTIONS                       .sz~ppressoi-wirh added \\.ords to ciran- attention
                                        i                        ihe
                         Fort~inately. n d u s q ha recogi~~zeil prob-              to the mo-port system.
                         lem and offen 3 line of devices spec~all!-                     To place the operation of 3 surge equalizer in
                         designed to pl-ocect against rliose spec~al.  but          perspeitlve, visualize the m-o p o ~ r s the
                                                                                                                             of
                         pre\ alent. surge pl-ohlems. Tlxs t> pe of deuce           equipment and their ground rekrences, as In
                         can be recognized easdy because it lm i 11 m               F ~ g ~ i r e During a surge event on one sys-
                                                                                                1.21.
                                 ~t
                         i n p ~ line cord with output ponei ieceptacles                            s
                                                                                    tem. there 1 a transient unhdr~ncebetn.een the
                         and (21 m telephone modular i;icIis (or \.idea
                                     o                                              m-o input references. wlhich c m be made worse
                         coax connectors) to insert In the telepllone con-          n hen thc seivice entrances a]-eat opposite ends.
                         nectlon (or video cable connection) The PI-ope1            I n a e r t q an SRE lust behind the T'v' set almost
                         engineering term for this ilev~ce .iii/::e I-efev-
                                                            IS                      re-establishes a balance between the m-o ports
                         euce eqz~nlizev   (SRE). but here again, popular                                          be
                                                                                    The ideal sltuation wo~~lcl to first h a w the
                         usage has not 3dopted the eng~neerlng      jargon          m;o sen-lces on the same s d e . and as 3 finlsl-iing
                         and rlie device is often called slmpl>-J s z ~ i g e       toach still provide an SRE




 Power                                                                                       Yideo
                                                                            Video

                Bad                                           Better                                                      Best


FIGURE 1.21: Shifting reference potential can be remedied by inserting a surge reference equalizer on the communications and
power lines (here, the appliance is a TV and the communications line is a TV cable, but a PC with a telephone modem connection
presents the same problem). In the ideal situation, the communications and power lines enter the house on the same side, and
the SRE is most effective.
                                                                                                          Q u e s t ~ o n st o A s k   -   23




                In This Section Customer-owned offenders; how to use the worksheets; identiFying residential
                and commercial appliance categories; Worksheet EDE: electronic, dual, external; Worksheet EDI:
                electronic, dual, internal; Worksheet ES: electronic, simple; Worksheet HE: heat, electronic;
                Worksheet HM: heat, mechanical; Worksheet ME: motor, electronic; Worksheet MM: motor,
                mechanical; Worksheet PLC: Power line conditioning


                This part of the manual is intended to facilitate     but other problems require a visit to the doctor's
                the interactions between a customer and a coop-       office and even a referral to a specialist.
                erative's service representative in tracking down        While the main thrust of the manual is the
                the cause of malfunction or damage and offering       effect of the utility supply on equipment-with
                remedies when possible. Hopefully, this proce-        the equipment characterized as "victim"-there
                dure will serve the common interests of both          are also cases of disturbed equipment that are
                parties, but, as a note of caution, not all prob-     associated with the customer's own operations
                lems can be solved over the telephone, and in         where some other equipment can be character-
                some cases it might be necessary to call in a         ized as a troublemaker or "offender." These
                power quality specialist to study the problem         offenders are listed in Table 2.1, for a quick
                and identify possible solutions, just as some         check that the reported problem does not fall in
                medical problems can be described over the            that category, so that the dialogue can then
                telephone to the family doctor and a suitable         focus on the suspected interaction between the
                prescription be picked up at the local pharmacy,      utility power supply and the equipment problem.



CustomerOwned   some appliances generate distur-       TABLE 2.1: Home-Based Disturbances, Causes, and Remedies
                bances that can cause a malfunc-
Offenders       tion of other appliances in the            Disturbance                 Cause                            Remedy
                same installation, or even in
                                                        TV remote disabled    Interference from                  Change type of lamp
                neighbors' installations. These
                                                        when lamp is on       fluorescent lamps
                disturbances are not attributable
                to the utility, but an uninformed                lamps
                                                         Fi~ckermg            Load cycling [electric             Plug loads in other
                customer might still make it a                                skillet, laser ~ r i n t e r )     branch circuits
                subject of complaint to the utili-
                ty. Table 2.1 describes typical
                disturbances, their causes, and
                possible remedies.
24 - S e c t i o n Two




HOW to Use               The procedure of troubleshooting consists of              3. Obtain from the customer as much back-
                         the following steps:                                         ground information as possible, using
the Worksheets                                                                         Part A of the worksheet as a script for
                           1. Obtain from the customer a description                   the dialogue.
                              of the victim equipment, and categorize              4. Reviewing the information thus obtained,
                              the type, using Table 2.2, a list of appli-              ask further questions as appropriate
                              ances likely to be found in residential                  according to Part B of the work sheet.
                              and small-business installations.                    5 . Present to the customer a tentative diag-
                           2. Turn to the diagnostic worksheets corre-                 nostic and possible remedy (some prob-
                              sponding to the type of victim equipment                 lems might be beyond simple remedies).
                              identified in step 1.The worksheets are
                              structured in three parts:
                              a) History and symptoms
                              b) Tentative diagnostics and remedies
                              C) Disposition of case



Identifying              For the purpose of narrowing the tentative diag-        the following codes in Table 2.2.
                         nosis, Table 2.2 lists several categories of equip-
Residential and
                         ment victims. To allow good understanding                 1. Motor, mechanical     MM
Commercial               between the customer and the service representa-          2. Motor, electronic:    ME
Appliance                tive, it will be useful to pin down, early in the d m     3. Heat, mechanical:     HM
                         logue, what is the specific appliance category to         4. Heat, electronic:     HE
Categories
                         be discussed. When the category is thus pinned
                         down, the "script" for the dialogue can be found        ELECTRONIC (COMMUNICATIONS) APPLIANCES
                         in one the the eight work sheets at rhe end of the      This generic category includes telephones, audio
                         manual. The customer representative should pho-         and video equipment, and personal computers.
                         tocopy blank work sheets and keep a supply of           Here again, two types must be recognized:
                         them to be filled in as the dialogue progresses,
                         then file them for future reference or additional         1. Appliances with a simple, one-link con-
                         review. For easy reference to the corresponding              nection to a power system (or to a tele-
                         work sheet, the categories identified by the table           phone system for simple sets).
                         are associated with a code that appears in bold           2. Appliances with a dual connection to both
                         type on the top right comer of the work sheet.               power and communication. Such appliances
                                                                                      can be subdivided further into two types:
                         MOTOR-DRIVEN APPLIANCES AND HEATING                          a) Appliances that are powered as well as
                         APPLIANCES                                                      linked to an external communication
                         For each category (motor-driven or heating),                    system such as telephone line, rooftop
                         there can be two or more types, depending on                    antenna, cable TV, or satellite dish. The
                         the type of control used:                                       exposure of this type of appliance is
                                                                                         significant because surges of external
                           Mechanical control (on-off, rotary, etc.-                     origin can come in through either the
                           no sophisticated keypad or other electronic                   power line or the communication link.
                           control)                                                      They can be caused by system distur-
                           Electronic control (keypad, display, etc.)                    bances or by remote lightning strokes.
                                                                                      b) Appliances that are powered as well as
                         These different controls influence the tentative                linked to an internal communication
                         diagnosis. Consequently, motor-driven and heat-                 system, such a garage door opener,
                         ing appliances are divided into four kinds, with                burglar alarm, intercom, thermostat, or
                                                                                                          Q u e s t i o n s t o Ask   -   25




         computer-controlled appliance. The                               The absence of a communication link, or the
         exposure of this type of appliance,                           type is a link is present, will influence the diag-
         even though it involves two systems, is                       nosis. The types of electronic appliances can be
         lower than that OF systems with exter-                        assigned these codes in Table 2.2:
         nal links. Disturbance or damage asso-
         ciated with the internal communication                           Electronic, simple:         ES
         links is limited to the rare case of a                           Electronic, dual, external: EDE
         very close lightning stroke Inducing a                         * Electronic, dual, internal: ED1
         voltage in those internal links.
                                                                        POWER LINE CONDITIONING EQUIPMENT
                                                                        Surge suppressors and un~nterruptiblepower
                                                                        supplies are given the code PLC in Table 2.2.


rABLE 2.2: Categories of Equipment Victims
                                                                 Codes:
                EDE = electron~c, dual, external                                        HM =    heat, mechanical
                ED1 = electronic, dual, internal                                        ME =    motor, electronic
                ES = electronic, simple                                                 MM=     motor, mechan~cal
                HE = heat, electron~c                                                   PLC =   power line conditioning

                  Appliance                        I                 Category as victim                    I       Work sheet

Air conditioner, central, conventional                     Motor, mechanical                                       MM
Air conditioner, central, variable speed                   Motor, mechanical                                       MM
                                                           Electronic, dual, internal                              ED1
Air conditioner, window                                    Motor, mechanical                                       MM
Antenna rotating system                                    Electronic, dual. external                              EDE
Attic fan, thermostat controlled                           Motor, mechanical                                       MM
                                                           Electronic, dual, external                              ED I
Automatic lawn sprinkler                                   Electronic dual, external                               EDE
Boom box                                                   Electron~c,simple                                       ES
Burqlar alarm, telephone link                              Electronc dual, external                                EDE
Burolar alarm, indeoendent
                  --
                                                   1       Electronic dual, internal                        1      ED1
Cell phone charger                                         Electronic, simple                                      ES
Central computer for business                              Electronic, dual, external                              EDE
Centrex telephone system                                   Electronic, dual, external                              EDE
Clock radio                                                Electronic, dual, simple                                ES
Clothes dryer                                              Motor, mechanical or electronic
                                                           Heat, mechanical or electronic
Coffee maker                                           I
                                                       I
                                                           Heat, mechanical                                    I

Computer network                                           Electronic, dual, external only or internal             ED1 or EDE
Computerized thermostat system                         1   Electronic, dual, internal                          I   ED1
 Dehumidifier                                              Motor, mechanical                                       MM
 Desktop publishing system                                 Electronic, dual, internal only or external             ED1 or EDE
26   -   S e c t i o n Two




                                 TABLE 2.2: Categories of Equipment Victims (Cont.)
                                                  Appliance                                      Category as victim                  Work sheet

                                 Digital clock, electronic                             Electronic, simple                            ES
                                 Digital clock, mechanical                             Motor, mechan~cal                             MM
                                 Digital video disk player                         I   Electronic, simple                        1   ES            I
                             I   Doorbell, sophisticated                           I   Electronic, dual, internal                I   ED1           1
                                 Distributed home entertainment system                 Electronic, dual, internal and external       €01and EDE
                                 Electric car battery charger                          Electronic, simple                            ES
                                 Exercise equipment                                    Motor, mechanical or electronic               M M or ES
                             I Fax machine                                         1   Electronic, dual, external                1   EDE           1
                                 Fire alarm system                                     Electronic, dual, internal and external       EDE and ED1
                             -
                                 Fluorescent lamp, compact                             Electronic, simple                            ES
                                 Fluorescent liqht, maqnetic ballast                   Heat, mechanical (eauivalent to]              HM
                             I   Fluorescent light~ng
                                                    system                         (   Electronc, dual, internal                 I   ED1           I
                             I   Fluorescent light, electron~cballast, single      I   Electronic, simple                        1   ES            I
                                 Food mixer                                            Motor, mechanical                             MM
                                 Freezer                                               Motor, mechanical                             MM
                                 Furnace                                               Motor, mechanical or electronic               M M or ME
                             1   Garage door opener                                1   Electronic, dual, internal                1   ED1           1
                                 Ground-fault circuit interrupter, receptacle          Electronic, simple                            ES
                                 Ground-fault crrcuit interrupter, service panel       Electronic, simple                            ES
                                 Ham radio, transmitter w ~ t h
                                                              antenna                  Electronic, dual, external                    EDE
                                 Ham radio, receiver without external                  Electronic, simple                            ES
                                 antenna
                             I Heat pump                                           /   Motor, mechanical or electronic           I   MMorME        I
                                 Hi-fi system, concentrated                            Electronic, simple                            ES
                                 Hi-fi system, distributed                             Electronic, dual, internal and external       ED1 and EDE
                                 Home security system, telephone link                  Electronic, dual, external                    EDE
                             I Hot water heater, isolated                          I   Heat, mechanical                          1   MA
                                 Hot water heater, computer controlled                 Heat, mechanical                              HM
                                                                                       Electronic, dual, internal                    ED1
                                 Humidifier                                            Motor, mechanical                             MM
                                 HVAC (heating, ventilating, and                       Electronic, dual, internal                    ED1
                                 air conditioninq) controls
                             (   Instant hot water for beverages                   I   Heat, mechan~cal                          1   HM            I
                             1   Intercom system                                   1   Electronic, dual, internal                I   ED1           I
                                 Llght bulb, incandescent                              Heat, mechanical                              MH
                                                                                        Cluestions t o Ask   -   27




rABLE 2.2: Categories of Equipment Victims (Cont.)
                 Appliance                  I                    Category as victim     I       Worksheet

Light d~mrner                               /           Electronic, s~rnple             I       ES
Microwave oven                              I           Electronic, simple              I       ES
Personal computer, isolated                 I           Electronic, simple              I       ES
Personal computer, telephone modem          1           Electronic, dual, external      I       EDE
Personal computer, cable modem                          Electronic, dual, external              EDE
Point-of-sale cash register                             Electronic, dual, external              ED1
Power tool                                              Motor, mechanical                       MM
Motion-detection lightng                    I           Electronic, simple              I       ES
Rechargeable flashlight/emergency Ighting   I           Electronic, simple              I       ES
Range, k~tchen                                          Heat, mechan~calor electronic           HM or HE
Refrigerator                                            Motor, mechanical                       MM
Satellite dish receiver                                 Electronic, dual, external              EDE
Sink disposal                                           Motor, mechanical                       MM
Sump pump                                       1       Motor, mechan~cal electron~c
                                                                        or              I       MMorME
Surge suppressor, permanent connection          1       Power line conditioner          I       PLC
Surge suppressor, plug-in                               Power line conditoner                   PLC
Surge suppressor, service entrance                      Power line cond~toner                   PLC
Surveillance camera system                              Electronic, dual, external              EDE
Telephone answering machine                             Electronic, dual, external              EDE
Telephone desk set, powered                     I       Electron~c,dual, external           1   EDE
Telephone desk set, simple                      /       Electronic, simple                  I   ES
Television receiver, cable input                I       Electronc, dual, external           I   EDE
Televis~onreceiver, rabbt ear                           Electronic, simple                      ES
Television receiver, satellite input                    Electronic, dual, external              EDE
Trash com~actor                                         Motor, mechanical                       MM
TVSS, permanently connected                     I       Power line conditioner              I   PLC
WSS, plug-in                                    I       Power lhne conditioner              I   PLC
WSS, surge reference equalizer                          Power line conditioner
                                                        Electronic, dual, external          I   PLC
                                                                                                EDE
Uninterruptible power supply                            Power line conditioner                  PLC
Vacuum cleaner                                          Motor, mechanical                       MM
Vacuum cleaner, central system                          Motor, mechanical                       MM
                                                        Electronic, dual, internal
Videocassette recorder, satellite input                 Electronic, dual, external              EDE
Videocassette recorder, cable input                 I   Electronic, dual, external          1   EDE
28   - Section   Two




                           TABLE 2.2: Categories of Equipment Victims (Cont.)
                                             Appliance            1             Category as victim          Work sheet

                       I Video conferencing                       I   Electronic, dual, external        I   EDE


                       I   Washer, dishes

                           Washer, clothes
                                                                      Motor, mechanical or electronic
                                                                      Heat, mechanical or electronic
                                                                      Motor, mechanical or electronic       HM or HE
                           Water well pump, submersed                 Motor, mechanical or electronic       M M or ME
                                                                      Electronic, dual, external            EDE
                       /   Water well pump, indoor, aboveground   1   Motor, mechanical or electronic   1   M M o r ME
                                                                                                       Questions t o Ask       -   29




                                          EDE
                                                     Worksheet EDE
                                                   Electronic, dual, external
A. HISTORY AND SYMPTOMS
Appliance identity                                                   Similar problem in neighbor's home?
    Name of customer                                                 0 Yes                                                     -
                                                                     0 No                                     -
   Appliance in question                                                Don't know                            -
 ]
C Where located in building?                                         Power system conditions
   Approximate a g e ? y e a r s                                        Apparently normal                     -
Symptoms                                                                Problem occurred in conjunction with:
   Quit working during normal operation                     -              A utility outage?
 ]
C Would not start when turned on                            -              Other incident?                    -
   Smoke came out                                           -              Describe:
   Acrid smell                                              -

   Blinking displays                                        -           Don't know                                             -
   Other                                                    -        System interaction
Has that condition happened before?                                     Proper bonding of power system and
   Previous repair history                                  -           communications system? (Y/N)                           -

   Did not report it                                        -             Surge reference equalizer
 ]
C Reported it but no action                                 -             installed? (Y/N)                        -
    Suggested action failed                                 -          Other information and remarks by customer:
    Don't know
Weather at the time of the problem
    Blue sky                                                -

    High winds                                              -

    Ice storm                                               -
    Distant thunder                                         -
    Local lightning                                         -
C ] Don't know                                              -


B. TENTATIVE DIAGNOSIS AND REMEDY
I Diagnosis                                             /   Remedy

I   System interaction [most likely). See under A.      I   Install surge reference equalizer.
    End-of-life burnout. (How old is equipment?)            Replace.
    Mechanical switch failure                               Repair
    Surge on the power line                                 Was there a surge reference equalizer? If yes, a temporay
                                                            overvoltane is likelv. If no, install surse reference esualizer.
I Temporan/ overvoltage                                 I   Repair if appliance is expensive, or replace.

C. DISPOSITION OF CASE
30   -   S e c t r o n Two




                                                                                   Worksheet ED1
                                                                                 Electronic, dual, internal
                             A. HISTORY AND SYMPTOMS
                             Appliance identity                                                     Similar problem in neighbor's home?
                                 Name of customer                                                   0 Yes                                                   -
                                                                                                       No                                                   -
                                    Appliance in question                                              Don't know                                           -
                                    Where located in building?                                      Power system conditions
                                Approximate a g e ? y e a r s                                          Apparently normal                                    -
                             Symptoms                                                                  Problem occurred in conjunction with:
                                Quit working during normal operation -                                     A utility outage?                                -
                                Would not start when turned on       -                                      Other incident?                                 -
                                    Smoke came out                                       -                  Describe:
                                    Acrid smell                                          -
                                Blinking displays                                        -             Don't know
                                Other                                                               Other information and remarks by customer:
                             Has that condition happened before?                                       How extensive are the communication links
                                Previous repair history                                  -             (garage antenna, intrusion switches, thermo-
                                    Did not report it                                                  stat controls, etc.)?
                                    Reported it but no action
                                    Suggested action failed
                                    Don't know
                             Weather at the time of the problem
                                Blue sky
                                    High winds
                                    Ice storm
                             17 Distant thunder
                                    Local lightning
                                    Don't know

                                 B. TENTATIVE DIAGNOSIS AND REMEDY
                                  Diagnosis                                              Remedy

                             (    End-of-life burnout. (How old is equipment?)       /   Replace.
                             I    Mechanical switch failure                          I   Repair
                                                                                                                  -          ~p




                                  Surge on the power line                                Was there a surge reference equalizer? If yes, a temporary
                                                                                         overvoltage is likely. If no, install surge reference equalizer.
                                  Temporary overvoltage                              I   Repair if appliance is expensive, or replace.

                                 C. DISPOSITION OF CASE
                                                                                                Lluestions t o Ask - 3 1




                                                Worksheet ES
                                                Electronic, simple
A. HISTORY AND SYMPTOMS
Appliance identity                                            Similar problem in neighbor's home?
    Name of customer                                          0 Yes                                                     -
                                                                 No                                    -
     Appliance in question                                       Don't know                            -
     Where located in building?                               Power system conditions
     Approximate a g e ? y e a r s                               Apparently normal                     -
Symptoms                                                         Problem occurred in conjunction with:
     Quit working during normal operation        -                  A utility outage?
     Would not start when turned on              -                  Other incident?                    -
     Smoke came out                               -                 Describe:
     Acrid smell                                  -
     Blinking displays                            -                Don't know                                           -
     Other                                        -             Other information and remarks by customer:
Has that condition happened before?
     Previous repair history                      -
     Did not report it                            -
     Reported it but no action                    -
     Suggested action failed                      -
     Don't know                                   -
Weather at the time of the problem
     Blue sky                                     -
     High winds                                   -
l"-J Ice storm                                    -
     Distant thunder                              -
     Local lightning                              -
     Don't know                                   -

B. TENTATIVE DIAGNOSIS AND REMEDY
 Diagnosis                                           Remedy

 End-of-life burnout, (How old is equ~pment?)        Replace.
  Mechanical switch failure                          Repair
  Surge on the power line                            Was there a surge reference equalizer? If yes, a temporary
                                                     overvoltage is likely. If no, install surge reference equalizer.
  Temporary overvoltage                          I   Repair if appliance is expenwe, or replace.

C. DISPOSITION OF CASE
32   -   S e c t i o n Two




                                                                              Worksheet HE
                                                                              Heat, electronic
                             A. HISTORY AND SYMPTOMS
                             Appliance identity                                           Similar problem in neighbor's home?
                                 Name of customer                                         0 Yes                                                     -
                                                                                              No                                                    -
                                Appliance in questlon                                     C] Don't know                                             -
                                Where located in building?                                Power system conditions
                                Approximate a g e ? y e a r s                                Apparently normal                     -
                             Symptoms                                                        Problem occurred in conjunction with:
                                Quit working during normal operation -                          A utility outage?                  -
                                Would not start when turned on       -                          Other incident?                    -
                                Smoke came out                       -                          Describe:
                                Acrid smell                          -
                                Blinking displays                    -                       Don't know                              -
                                Other                                -                    Other information and remarks by customer:
                             Has that condition happened before?
                             [7 Previous repair history              -
                                Did not report it                    -
                                Reported it but no action            -
                                Suggested action Failed              -
                                Don't know                           -
                             Weather at the time of the problem
                                 Blue sky                            -
                                 High winds                          -
                                 Ice storm                           -
                                 Distant thunder                     -
                                 Local lightning                     -
                                 Don't know                          -
                             B. TENTATIVE DIAGNOSIS AND REMEDY
                              Diagnosis                                          Remedy

                               End-of-life burnout. (How old is equ~pmentll      Replace.
                               Mechanical s w t c h failure                      Repair
                               Surge on the power line                           Was there a surge reference equalizer? If yes, a temporary
                                                                                 overvoltage is likely. If no, install surge reference equalizer.
                               Temporary overvoltage                             Repair if appliance is expensive, or replace.

                             C. DISPOSITION OF CASE
                                                                                            (luestions t o Ask - 3 3




                                                Worksheet HM
                                                Heat, mechanical
A. HISTORY AND SYMPTOMS
Appliance identity                                              Similar problem in neighbor's home?
    Name of customer                                            0 Yes                                          -
                                                                   No                                          -
   Appliance in question                                           Don't know                                  -
   Where located in building?                                   Power system conditions
   Approximate a g e ? y e a r s                                   Apparently normal                           -
Symptoms                                                           Problem occurred in conjunction with:
   Quit working during normal operation                               A utility outage?
   Would not start when turned on       -                             Other incident?                          -
   Smoke came out                       -                             Describe:
   Acrid smell                          -
C] Blinking displays                    -                          Don't know                              -
   Other                                                        Other information and remarks by customer:
Has that condition happened before?
   Previous repa~r  history             -
   Did not report it                    -
   Reported it but no action                         -
   Suggested action failed                           -
   Don't know
Weather at the time of the problem
   Blue sky                                          -
   High winds                                        -
   Ice storm                                         -
   Distant thunder                                   -
   Local lightning                                   -
   Don't know                                        -


B. TENTATIVE DIAGNOSIS AND REMEDY
I Diagnosis                                      /   Remedy                                                            I
 End-of-life burnout. (How old is equipment?)        Replace.
 Mechanical switch failure                           Repair
 Temporary overvoltage                               Repair if appliance is expenwe, or replace.

C. DISPOSITION OF CASE
34   -   S e c t i o n Two




                                                                              Worksheet ME
                                                                              Motor, electronic
                             A. HISTORY AND SYMPTOMS
                             Appliance identity                                              Similar problem in neighbor's home?
                                 Name of customer                                            0 Yes                                                -
                                                                                                No                                    -
                                Appliance in question                                           Don't know                            -
                                Where located in building?                                   Power system conditions
                                Approximate age?-years                                       0 Apparently normal                      -
                             Symptoms                                                        [7 Problem occulred in conjunction with:
                                Quit working during normal operation -                             A utility outage?                  -
                                Would not start when turned on       -                             Other incident?
                                Smoke came out                       -                             Describe:
                                Acrid smell                          -

                                Blinklng displays                                  -            Don't know                              -
                                Other                                              -         Other information and remarks by customer:
                             Has that condition happened before?
                                Previous repair history                            -
                                Did not report it                                  -
                                Reported it but no action                          -

                             C] Suggested action failed                            -
                                Don't know                                         -
                             Weather at the time of the problem
                                Blue sky                                           -
                              ]
                             C High winds                                          -
                             C] Ice storm                                          -
                                Distant thunder                                    -
                                Local lightning                                    -
                                Don't know                                         -

                             B. TENTATIVE DIAGNOSIS AND REMEDY
                               Diagnosis                                           Remedy

                               Mechanical overload                                 Check for jamming or seized bearing; clean out or repair.
                             I End-of-life burnout. (How old is equipment?)    I   Replace
                               Mechanical switch f a G                             Repair
                               Surge on the power line                             Was there a surge reference equalizer? If yes, a temporary
                                                                                              is
                                                                                   ove~oltage likely. If no, install surge reference equalizer.
                             I Temporary overvoltage                           I        if
                                                                                   Repa~r appliance is expensive, or replace.

                             C. DISPOSITION OF CASE
                                                                                             Q u e s t ~ o n st o A s k   -   35




                                                 Worksheet MM
                                                 Motor, mechanical
A. HISTORY AND SYMPTOMS
Appliance identity                                             Similar problem in neighbor's home?
    Name of customer                                           0 Yes                                                      -

                                                                    No                                    -
   Appliance in question                                            Don't know                            -
   Where located in building?                                    Power system conditions
   Approximate a g e ? y e a r s                                    Apparently normal                     -
Symptoms                                                            Problem occurred in conjunction with:
   Quit working during normal operation -                              A utility outage?                  -
   Would not start when turned on                     -
                                                                       Other incident?                    -
   Smoke came out                       -                              Describe:
   Acrid smell                          -
   Blinking displays                    -                           Don't know                                            -



   Other                                -                        Other information and remarks by customer:
Has that condition happened before?
   Previous repair history              -
   Did not report it                    -

   Reported it but no action                          -
   Suggested action failed                            --
   Don't know                                         -

Weather at the time of the problem
   Blue sky                                           -
   High winds                                         -

    Ice storm                                         -
    Distant thunder                                   -

    Local lightning                                   -

    Don't know                                        -


B. TENTATIVE DIAGNOSIS AND REMEDY
I Diagnosis                                       /   Remedy                                                                       I
  Mechanical overload                                 Check for jamming or seized bear~ng;clean out or repair.
  End-of-life burnout. (How old is equipment?)        Replace.
I Mechanical switch failure                       I   Repair

C. DISPOSITION OF CASE
3 6 - S e c t i o n Two




                                                                 PLC
                                                                         Worksheet PLC
                                                                       Power line conditioning
                          A. HISTORY AND SYMPTOMS
                          Appliance identity                                        Similar problem in neighbor's home?
                              Name of customer                                      0 Yes                                         -
                                                                                    0 No                                          -
                             Appliance in question                                     Don't know                            -
                             Where located in building?                             Power system conditions
                             Approximate a g e ? y e a r s                             Apparently normal                     -
                          Symptoms                                                  C] Problem occurred in conjunction with:
                             Quit working during normal operation -                       A utility outage?                  -
                             Would not start when turned on       -                       Other incident?                    -
                             Smoke came out                                 -             Describe:
                             Acrid smell                                    -
                             Blinking displays                              -           Don't know                                -
                          [7 Other                                          -        Other information and remarks by customer:
                          Has that condition happened before?
                             Previous repair history                        -
                             Did not report it                              -
                             Reported it but no actlon                      -
                             Suggested action failed                        -
                             Don't know                                     -
                          Weather at the time of the problem
                             Blue sky                                           -

                              High winds                                        -
                              Ice storm                                         -
                              Distant thunder                                   -
                              Local lightning                                   -
                              Don't know                                        -

                          6. TENTATIVE DIAGNOSIS AND REMEDY
                            Diagnosis                                            Remedy

                           Surge suppressor and uninterruptible power supply:    Replace
                              End-of-life burnout
                              Temporary overvoltage (most likely)
                              "Large" surge (quite rare)
                            Uninterruptible power supply only:                   Replace
                               Battery problem?

                          C. DISPOSITION OF CASE

								
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