CUST PQ EXPRNCE by FuzorePejal


									    1204                                               IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS , VOL. 29, NO. 6, NOVEMBEFUDECEMBER 1993

           Distribution Customer Power Quality Experience
                                         Brent M. Hughes, John S. Chan, and Don 0. Koval

      Abstract-In recent years there has been a significant increase         overlook the important consideration that electronic equipment
    in the number of disturbance producing loads and “sensitive”             is not designed to perform adequately in their mutual electrical
    loads being utilized by society resulting in increased customer          environments. A knowledge of the power quality characteris-
    complaints being directed at utilities. B.C. Hydro is taking a
    proactive approach i determining its own power quality by
                          n                                                  tics of a utility’s and customer’s electrical systems is essential
    monitoring voltage disturbances and harmonic levels dictated             for economical mitigating actions by both the utility and their
    by a power quality survey program. This paper will present               customers.
    and discuss in detail some of the key objectives of the power
    quality program. A methodologyfor quantifying power quality as
    experienced by customers in a graphical form will be presented.               11. POWER     SURVEY
                                                                                          QUALITY    GENERAL
    Several detailed case studies will be presented to illustrate the               B.C. Hydro, in the Province of British Columbia in Canada,
1   methodology. Estimating algorithms for the duration and mag-
    nitude of the various types of power supply disturbances will be              has initiated a two year power quality survey Program to
    developed and illustrated.                                                    determine the quality of power it delivers to its customers in
                                                                                  each of its geographical regions. Some of the major objectives
                                                                                  of the power quality monitoring program are:
                               I. INTRODUCTION
                                                                                     1) to correlate customer power quality with major causes
       The delivery of electrical energy is subject to various                          of utility generated disturbances;
    regulations (e.g., CSA CAN3-C235283: “Preferred Voltage                         2) to prepare power quality information for customers;
    Levels for AC Systems, 0 to 50,000 V”, ANSI (34.1-1977)                          3) to generate site voltage profiles (i.e., the magnitude
    specifying the upper and lower limits of the utilization voltage                    and duration of power supply voltage disturbances) and
    at the customer’s service entrance. Service voltage levels                          superimpose the ANSI/IEEE Std. 446-1987 “Electronic
    operating outside these limits are often called power supply                        equipment operating envelope” [2] onto the site voltage
    anomalies or power system disturbances. Historically, power                         profile to provide a reference framework.
    quality was not an issue of major concemto society. G .
    Bonnard [l] of Electricite de France (i.e., EDF) stated that                     When detailed statistical correlation studies of a sufficient
    ”the present supply is entirely adequate for the majority of number of site surveys have been completed, a primary objec-
    electrical power uses. However, electronic power equipment tive of the power quality program will be predicting customer
                                                                                  power quality given the characteristics of the customer’s utility
    creates a dual problem for the utility:
           firstly, this equipment, in common with any device supply.
           incorporating electronic components, is sensitive to volt-
           age dips and short voltage variations (i.e., power supply                      111. POWER QUALITY MONITORING         PROGRAM
           secondly, this type of equipment generates harmonic                       A distribution feeder ranking index was developed to select
           distortion, and under certain conditions can pollute the customer sites for the monitoring program. Once a site was
           network to a degree no longer acceptable by all cus- selected, the monitors were connected to the customer’s 120
           tomers.”                                                               volt service entrance. The voltage characteristics at a given site
                                                                                  are continuously monitored for a one month period and the
       Society’s economical survival is dependent upon the per-
                                                                                  harmonic distortion levels continuously monitored for a one
    formance of their motorized and computerized devices. When
                                                                                  week period. In addition to monitoring customer sites, primary
    power supply anomalies “allegedly” curtail the performance metered locations were continuously monitored to evaluate the
    of these devices, the economic benefits of this technology are
                                                                                  power quality of the distribution primary feeders.
    quickly eradicated and many problems arise for both the utility
                                                                                     The monitoring devices selected for the program [3] were:
    and their customers. The utility often states the origins of the
    power supply disturbances are at the customer’s site, while
                                                                                     - 10 BMI 2460 disturbance monitors
                                                                                     - 5 BMI 3060 harmonic monitors
    a utility’s customers claims the origins are located within
    the utility electrical system. Often in their discussions, they                  Some of the key monitor requirements at the time of
                                                                                  selection were:
      This paper was presented at the 1991 Industry Applications Society Annual
    Meeting, Dearbom, MI, September 28-October 4.                                    1) automatic restart following a power outage
      The authors are with Powertech Labs Inc., 12388-88th Avenue Surry, B.C.        2) floppy disk storage
    V3W 7R7 Canada.                                                                  3) ability to readprocess the surveyed data on disk with
       B.C. Hydro, 5345 Goring Street, Bumaby, B.C., V5B 3A2 Canada.
       Dept. of Electrical Engineering, University of Alberta, Edmonton, Alberta,       in-house computer programs
    T6G 2G7 Canada.                                                                  4) inexpensive and easy to use.
                                                           0093-9994/93$03.00 0 1993 IEEE
HUGHES et al.: DISTRIBUTION CUSTOMER POWER QUALITY EXPERIENCE                                                                                                                1205

                              TABLE I                                                       T h e (%)
                                      THRE~HOLDS                                      100

DISTURBANCE TYPE                      THRESHOLD SETTINGS                               80
Surge                                 > 150 volts peak
Waveshape Fault                       > f25 volt peak change                           60
Sag                                   < 110 volts rms
Swell                                 > 125 volts rms                                  40
Outage                                0 volts rms



                          \ 1
                      Surge          Waveshape         Swell
                                                                                         100          105    110        115       120
                                                                                                                              Voltage (V)
                                                                                                                                          125       130

                                                                             Fig. 3. Cumulative relative frequency histogram of site rms voltage levels.
                                                                                                                                                                135    1,

                \I   I                  Fault

         2 o o % t d I                                          I                        Voltage (Vrms)


                                                                                                                                     End of outage.
                                                                                                                                   /Monitor turns on.
         100%                                                                         1501

                               Disturbance Duration                                                    Start of outage.

                                                                                       501              after 5 minutes.
 Fig. 1. Duration boundaries of the various types of voltage disturbances.

                                                                                          0       2      4    6     8     10 12 14 16               10     20     22    24
                                                                                                                        The-of-Day (hr)
                                 Hlgh Voltage
         135 -                                                                                  Fig. 4 Magnitude and duration of an outage.
         130 -
         125 ....................................
              ...................................               I                     140

                                                                                      135 -
                                                                                             . . . . .--IF. . . . . . . . . . . . . . . . . . . . . . .
                                                                                      125 _ . . . . . . . . . . . . . .* . . . . . .r. . . . . . . . . . . . .
                                                                                                       .....           .
                                                                                                             ,    ,          m                  1           V

         105 -                                                                        120 -
                                 Low Voltage
                                                                                      110 ...................................

 Fig. 2. Steady state rms voltage levels as a function of the time of day.            105 -


  The types of disturbances and threshold levels used in the
power quality survey program are listed in Table I.
  The duration boundaries for the various types of distur-                                                                                                                          ,
                                                                             than a specified level. These site frequency histograms provide
bances are illustrated and defined in Fig. 1.
                                                                             empirical evidence of the design and operating characteristics
                                                                             of a utility's electrical distribution system and its customer's
                                     LEVELS                                  electrical facilities.
   B.C. Hydro's power quality site surveys capture a site's rms
voltage levels as a function of the time of day as illustrated                                                        PROFILE
                                                                                                        V. SITE VOLTAGE
in Fig. 2. These detailed plots provide insight into the daily                 In order to represent all of the various types of power
variations of voltage levels at a given site both as a function of           supply disturbances on a single site voltage profile (i.e.. a
time and the distribution system and customer loading patterns.              plot of the magnitude of site voltage level and the duration
Excursions of voltage levels outside standardized limits can                 of its occurrence), it is necessary to define the duration and
be correlated with the activities occurring within the utility's             magnitude of each type of monitored disturbance. For some
distribution system and customer's electrical facilities that                types of disturbances, this task is relatively easy. For example,
caused these non-compliant events.                                           the magnitude and duration of an outage, voltage swell, voltage
   A more compact form of representing the steady state rms                  sag and voltage waveshape fault are illustrated in Figs. 4, 5,
site voltage levels is to express them in the form of a relative             6 and 7, respectively. However, for voltage surges the task is
and cumulative frequency histogram as illustrated in Fig. 3.                 more complicated because the monitor in the power quality
The frequency histogram provides a visual description of the                 program does not define the duration of the voltage surge but
variance in site voltage levels as well as a probability level               provides sufficient site information to estimate the duration of
that the site rms voltage level will be less than or greater                 a voltage surge.
    1206                                                     IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS , VOL. 29, NO. 6, NOVEMBERDECEMBER 1993

                                                                                              Voltage (V)
              140                                                                         200 I

              135 -

              130 -                                                                       100
               ,26     ...................................
               120 -                                                                        0


                                                                                             0          20        40      80       80      100          120
                                                                                                                       Tlme (ms)

                                                                                           Fig. 8. Voltage surge onsinusoidal voltage supply.

                      Voltage (VI                                                               Voltage (V)
               200 I                                                I
                                                                                                I -. I
                                                                                          100 -


                                                                                                           ,DUratio;        1[
                                                                                                                           , I             MI


                                                                                                                                                  * I

               -200   I                                             I                   -200
                      0        20   40      eo       80   100      120                          0       20        40      80       80      100          120
                                         Time (ms)                                                                     Tlme (us)

            Fig. 7. Magnitude and duration of a voltage waveshape fault.                Fig. 9. Equivalent and actual voltage surge waveshape.

                        THE     OF                                                 The above constraints can be expressed in the following
       A voltage surge captured by the power line monitor is shown               mathematical forms:
    in Fig. 8. In the analysis of voltage surges, the sinusoidal                   1) The peak surge voltage value occurs at t m = 1 . 5 , and
    portion of the waveform is stripped from the recorded wave-                       dw(t)/dt = 0.0 resulting in the following mathematical
    form resulting in the surge waveform as illustrated in Fig. 9.                    expression:
    The monitoring instrument used in the power quality survey
    program reports the peak value of the voltage surge and its                                     dw(t)/dt = d/dt(Vm(e-At - e-Bt))                          (2)
    energy content assuming a constant impedance. The duration
                                                                                       Solving for B as a function of A yields:
    of the voltage surge is not reported and must be estimated for
    the inclusion of voltage surges on a site’s voltage profile.                                                           1nA - In B
       A monitored voltage surge can be approximated by the
    following generalized double exponential function:
                                                                                                              ’=A-(           tm          )                   (3)

                                                                                      where: t m = 1 . 5 ~ s
                               w(t) = Vm(e-At - e--Bt)                     (1)     2) The maximum value of the theoretical surge voltage
    where:                                                                            which occurs at t = t m = 1 . 5 ~ s
                                                                                                                        must equal the peak
    w(t)-theoretical surge voltage as a function of time                              voltage recorded by the power disturbance monitor and
    Vm-maximum exponential voltage                                                    can be expressed as:
    A-energy time constant                                                             Vp(monitored) = w(t) = Vm(e-Atm - e--Btm)                              (4)
    B-“time to peak” time constant
      The above equation has three unknown variables, namely,                      3) The theoretical energy content of the voltage surge must
    A, B and Vm which can be evaluated from known constraints                         be equal to the energy level recorded by the monitor and
    dictated by the two monitored surge parameters, i.e., the                         can be expressed by the following equation:
    magnitude of the peak surge voltage and its energy content
    and a reported impedance.
      The following constraints are imposed on equation (1):
                                                                                                       E(monitored)Z =             lz0

                                                                                                                                        v(t)2dt               (5)

       1) the theoretical voltage v(t) peaks at 1.5 ps.                                where: 2- impedance
      2) the maximum value of the theoretical surge voltage                        Integration of the above equation results in the following
          must equal the peak voltage recorded by the monitoring                 expression for A:
      3) the theoretical energy content of the voltage surge must                    A=
                                                                                                      BVm2(A B )            +                                 (6)
          equal the energy reported by the BMI instrument.                                 2BZE(monitored)(A B ) Vm2(A     + +                      + B)
HUGHES et al.: DISTRIBUTION CUSTOMER POWER QUALITY EXPEFUENCE                                                                                 1207

   The three unknowns in equation (1) can be solved from                                    TABLE II
equations 3, 4 and 6 using an iterative solution methodol-               SITE MONITORING IDENTIFICATION-RESIDENTIAL SITE
ogy until convergence occurs, assuming the following initial        GENERAL INFORMATION                    SPECIFIC DETAILS
estimates:                                                          City                                   Langley, B.C.
                                                                    Feeder                                 MLN 25F63
               Vm = Vp(monitored)                                   Customer Type                          residential
                  A = Vm2/2E(monitored)Z                            Primary/secondary metered              secondary
                                                                    Monitoring duration                    1729 channel hours
                  B = 3 x lo6
   The value of B is an expected value that was obtained from
many field results. As more surveys are conducted the initial                       Time (%)
guess may change, but not significantly.                                                                                 High Voltage
   For example, if the monitored peak value of the voltage
surge was -241 volts and the energy content of the voltage
sure 10 Joules with a source impedance of 1.0 ohm, the
iterative solution for the unknown variables A , B and Vm                     40%
of the theoretical surge voltage equation are:

                    A = 2927.943                                               0%
                                                                                 100     105   110   115   120     125   130    135      1
                                                                                                                                        1 I
                    B = 4959421.                                                                     Voltage (V rms)
                   Vm = -242.2038 volts                             Fig. 10. Residential rms voltage level relative and cumulative frequency

   The duration of the voltage surge is assumed to begin with
                                                                                           TABLE III
the initiation of the voltage surge and end when the value of                      WITH
                                                                          COMPLIANCE CSACAN3-%25-83:"pREFERRED    VOLTAGE
the voltage surge reaches 50% of the peak value which occurs              LEVELS AC SYSTEMS, 0 T 50000V" - RESIDENTIAL SITE
                                                                               FOR              O
at time (t(50%)).  The duration t(50%) expressed in equation 7                                             % OF TIME VOLTAGE LEVELS
can be solve iteratively to determine the duration of a voltage     VOLTAGE LIMITS                         WITHIN/OUTSIDE LIMITS
surge.                                                              Normal Operating Conditions            100.0
                                                                    [ 1 10- 125V]
                                                                    > 125 volts                            0.0
 t(50%) = -1/A{ln((V(monitored)/2Vm)           +                    < 110 volts
                                                                    Extreme Operating Conditions
                                                             (7)    [ 106-127Vl
For the above example, t(50%) = 238.4 ps                            > 127 volts                            0.0
                                                                    < 106 volts                            0.0
                                                                    Site voltage rms average               121.3 volts
                                                                                           TABLE N
   The B.C. Hydro power quality survey program summarizes                            OF         OF
                                                                            FREQUENCY OCCURRENCE THEV m o u s TYPESOF
the power quality statistics at each site as follows                       VOLTAGE         MONITORED A RESIDENTIAL
                                                                                 DISTURBANCES      AT             SITE.                              ,
   1) site monitoring identification table                          TYPE OF VOLTAGE                        FREQUENCY OF
  2) site r.m.s. voltage level relative and cumulative fre-         DISTURBANCE                            OCCURRENCE
                                                                    Surges                                 0
      quency histograms                                             Waveshape                              1
   3) site r.m.s. voltage level compliance table                    Swells                                 3
  4) site frequency count table of the various types of mon-        Sags                                   5
      itored disturbances                                           Outages                                0
  5) site voltage profile
   6) a site voltage total harmonic distortion frequency his-
      togram                                                           For this particular residential site, the steady state rms
   An example of the documentation of a residential, commer-        voltage levels complied with CSA standards.
cial and industrial site survey will be presented next.                The frequency of the various types of voltage disturbances
                                                                    monitored at the residential site during a 1729 hour monitoring
                                                                    period are listed in Table IV.
VIII. POWER QUALITY                1                                   The duration and magnitude of the various types of voltage
  The details of an illustrative residential power quality survey   disturbances monitored at the residential site are plotted on
are summarized in Table 11.                                         a site voltage profile shown in Fig. 11. The CBEMA curve
  A steady state rms site voltage histogram is shown in Fig.        [ 11 is superimposed onto the site voltage profile as a reference
10 and the critical results summarized in Table 111.                frame and is not intended to be used to assess the susceptibility

    1208                                                      IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 29, NO. 6, NOVEMBERiDECEMBER 1993

                  Magnitude (% nominal)                                                          Time (%)
              350%I                                                                       innr.
                              \                                       I

              2%                                                                           60%



              o %
              l50% %
                                                                                                100    105       110   115    120    125   130     135     140
                                                                                                                        Voltage (V rms)

                                                                                 Fig. 13. Commercial rms voltage level relative and cumulative frequency

                                                                                                           TABLE VI
                                                                                       COMPLIANCE WITH CSACAN3-C25-83:"PREFERRED
                                                                                       LEVELSFOR Ac SYSTEMS, To 50000V - COMMERCIAL
                                                                                                            0                      SITE
              o %
              l o %
                                                                                                                             % OF TIME VOLTAGE LEVELS
                                                                                 VOLTAGE LIMITS                              WITHIN/OUTSIDE LIMITS
               60%                                                               Normal Operating Conditions                 99.8
               40%                                                               > 125 volts                                 0.0
                                                                                 < 110 volts                                 0.2
               20%                                                               Extreme Operating Conditions                99.1
                                                                                 [ 106-127V]
                                                                                 > 127 volts                                 0.0
                O%O%    1%   2%    3% 4% 5% 6% 7% 6%
                                  Total Harmonic Distortion (%)
                                                                  9% 10%         < 106 volts                                 0.1
                                                                                 Site voltage rms average                    119.9 volts
           Fig. 12. Residential total percent voltage harmonic distortion.

                                TABLE V                                                                   TABLE VI1
                 SITEMONITORING                                                           FREQUENCY OCCURRENCE THE VARIOUS
                                                                                                    OF         OF          TYPESOF
                                                                                                          MONITORED A COMMERCIAL SITE.
                                                                                        VOLTAGE DISTURBANCES        AT
                                            Coquitlam, B.C.                      TYPE OF VOLTAGE                             FREQUENCY OF
    Feeder                                  COK 25F811                           DISTURBANCE                                 OCCURRENCE
    Customer Type                           commercial                           Surges                                      391
    Primarylsecondary metered               secondary                            Waveshape                                   26
    Monitoring duration                     2074 channel hours                   Swells                                      0
                                                                                 Sags                                        28
                                                                                 Outages                                     0

    and performance of "sensitive" electronic equipment, a subject
                                                                                              Magnitude (% nominal)
    which requires significantly more research. It is clear from                          350%
    Fig. 11 that all of the voltage disturbances were confined to                                                \if
    the interval [ 100 ms to 1 second]. The customer expressed no                         300%
                                                                                                                 * b?%
    complaints concerning the quality of their electric service.                          250%
      The total voltage harmonic distortion expressed as a per-
    centage for the residential site is shown in Fig. 12. The total
    habonic distortion level averaged 2.6% and was typical of
    many residential sites.

                    SITE           2                                                        0     %   m      n   a a ~ i a b ~s& c m   a a G n A L a * 8si*L
                                                                                                                 Disturbance Duration (Seconds)
       The details of an illustrative commercial power quality                                        Fig. 14. Commercial voltage profile.
    survey are summarized in Table V.
       A steady state rms site voltage histogram is shown in Fig.                  The frequency of the various types of voltage disturbances
    13 and the critical results summarized in Table VI.                          monitored at the commercial site during a 2074 hour monitor-
       For this particular commercial site, the steady state rms volt-           ing period are listed in Table VII.
    age levels were outside the CSA standard extreme operating                     The duration and magnitude of the various types of voltage
    limits 0.1% of the time. These voltage excursions outside the                disturbances monitored at the commercial site are shown in
    limits were attributed the refrigerator motor activities on site.            Fig. 14, a voltage profile of the site. Note the significant
    HUGHES et al.: DISTRIBUTION CUSTOMER POWER QUALITY EXPERIENCE                                                                                         1209

                                                                                               Time (%)



                                                                                               100   105    110    115    120    125   130    135   140
              ‘0%                                                                                                   Voltage (V rms)
                 0%   in   2%    3%     4n 5 2 6% 7 n 8%        9%   ion
                                Total Harmonic Dlstortlon (%)                  Fig. 16. Industrial rms voltage level relative and cumulative frequency his-
       Fig. 15. Commercial total percentage voltage harmonic distortion.                                         tograms.

                            TABLE VIII-A                                                                    TABLE IX
               SITE MONITORING           - INDUSTRIALSITE                                FREQUENCY OCCURRENCE OF THE VARIOUS TYPESOF
                                                                                            SITE VOLTAGE DISTURBANCES- INDUSTRIAL SITE.
                                          Galloway, B.C.                       TYPE OF VOLTAGE                           FREQUENCY OF
    City                                                                       DISTURBANCE                               OCCURRENCE
    Feeder                                WIN 25F52
                                                                               Surges                                    6
    Customer Type                         Industrial
                                                                               Waveshape                                 0
    Primarykcondary metered               secondary
    Monitoring duration                   125 channel hours                    Swells                                    33
                                                                               Sags                                      829
                                                                               Outages                                   0

                        TABLE VIII-B
                   WITH                      VOLTAGE
               FOR         0                     SITE

    Normal Operating Conditions
               ;                      :   43.5
                                          % OF TIME VOLTAGE LEVELS
                                          WITHIN/OUTSIDE LIMITS            :             :      Magnitude (% nominal)

    > 125 volts                           52.0
    < 110 volts                           4.5
    Extreme Operating Conditions          78.4                                           150%
    [106-127V]                                                                           100%
    > 127 volts                           20.4
    < 106 volts                           1.2                                                50%
    Site voltage rms average              125.0 volts

                                                                                                             Disturbance Duration (Seconds)

                                                                                                     Fig. 17. Industrial voltage profile.
    difference between the residential and commercial voltage
       The total voltage harmonic distortion expressed as a per-      The frequency of the various types of voltage disturbances
    centage for the commercial site is shown in Fig. 15. The total monitored at this commercial site during the 125 hour monitor-
    harmonic distortion level averaged 1.4%for this site.          ing period are listed in Table IX. Note the significant difference
                                                                   in the pattems of voltage disturbances monitored at the resi-
                                                                   dential and commercial sites compared to this industrial site.
      X. POWER     QUALITY   SITESURVEY    NUMBER INDUSTRIAL The duration and magnitude of the various types of voltage
                                                                   disturbances monitored at this industrial site are plotted on
       The details ,of an illustrative power quality survey at an
                                                                   a site voltage profile as shown in Fig. 17. The customer
    industrial site are summarized in Table VIII-A.
                                                                   expressed no complaints concerning the quality of their electric
       A steady state rms site voltage histogram is shown in Fig.
    16 and the critical results summarized in Table VIII-B.
                                                                      The total voltage harmonic distortion expressed as a per-
       The voltage profile revealed voltage levels outside the CSA
                                                                   centage for this industrial customer is shown in Fig. 18. The
    limits for a significant portion of the time. This industrial
                                                                   total harmonic distortion level averaged 2.8%.
    customer was on a “weak” feeder. The high voltage conditions
    occurred during light load periods from during the night and
    on weekends. The low voltage conditions occurred during                                 XI. CONCLUSION
    extremely heavy load periods at the site. Despite this “poor”     This paper has presented a methodology for quantifying
    voltage profile, the customer did not complain about the power customer power quality that has been adopted by B.C. Hy-
    quality being experienced at their site.                       dro’s Power Quality Survey Program. The objectives of the


1210                                                           IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS , VOL. 29, NO. 6, NOVEMBEFUDECEMBER 1993

                                                                                  the magnitude and duration of the disturbance except for
                                                                                  waveshape faults. An algorithm was developed for finding the
                                                                                  duration of waveshape faults and the results illustrated in the
                                                                                     A voltage profile showing the magnitude and duration of all
                                                                                  monitored voltage disturbances for a residential, commercial
                                                                                  and industrial site survey was presented in this paper. Despite
                                                                                  the extreme differences in the site voltage profiles, each of
                                                                                  the three customers were satisfied with their quality of power.
                                                                                  An other important conclusion concerning these examples is:
                                                                                  each site is unique.
                           Total Harmonic Distortion (%)                             A frequency histogram of the total voltage harmonic distor-
       Fig. 18. Industrial total percentvoltage harmonic distortion.              tion levels at each site was presented. These graphs provide
                                                                                  a reference frame for both the customer and the utility and
                                                                                  enable both parties to assess the impact of changing customer
proactive power quality program are listed and discussed in                       loads and changing harmonic levels within the distribution
detail in the paper. For each site monitored, the power quality                   system and at various customer sites.
site characteristics are summarized by three graphs:                                 Approximately 90 site surveys have been conducted to date.
   1) a steady state rms voltage level relative and cumulative                    The large volumes of power quality data collected for each
       frequency histogram                                                        site survey are stored on computer disks for further statistical
   2 ) a voltage profile showing the magnitude and duration                       analysis. This large data base is being analysed in detail
       of all voltage disturbances captured during the site                       to provide power quality indices and voltage and harmonic
       monitoring period                                                          profiles for:
   3) a frequency histogram of the total voltage harmonic                            1) individual customers
       distortion monitored at a site.                                               2 ) various customer classes
   These graphs provide customer information on the quality of                       3) individual distribution feeders
their electrical power and provide a data base for economical                        4) individud,distribution substations
mitigation actions, empirical evidence of utility performance                        5) geographical areas.
and a means for assessing the impact of customer loads on
their own power quality.                                                                                        REFERENCES
   Steady state rms voltage level relative and cumulative
                                                                                       Bonnard, G., “Electricity Supply to Electronic. Power Ekpipment-
frequency histograms and a table showing the percentage of                             Environmental Factors”, IEEE Conf. Publ. 234, 1984, pp. 2627-2631.
the time the voltage remains within CSA standard limits are                            ANSUIEEE Std. 446-1987: IEEE Recommended Practice for Emergency
prepared for each site survey. The percentage of the time a                            and Standby Power Systems for Industrial and Commercial Applica-
                                                                                       tions, (IEEE Orange Book).
site’s voltage levels are non-compliant is also presented. The                         McEachern Alexander, Handbook of Power Signatures, 1988, published
important point to note in non-compliant cases is that voltage                         by: Basic Measuring Instruments, 335 Lakeside Drive, Foster City,
excursions outside the standardized limits can be caused                               Ca..94404, U.S.A.
                                                                                       Palladino T., Koval, D. 0.. “Identifying the Possible Origins of Power
by activities originating within the utility’s electrical system                       System Disturbances Caused by a Utility’s Operations”, Proceedings of
and/or within the customer’s electrical facilities. Detailed                           the 18th Annual Pittsburgh Conference on Modeling and Simulation,
feeder analysis and site investigation are required to identify                        Vol. 8, Part 2, April 23-24, 1987, pp. 573-578.                             ,
                                                                                       Allen, G. W. and Segall, D., “Monitoring of Computer Installations
the origins of steady state non-compliant site voltage levels.                         for Power Line disturbances”, IEEE PES Winter Meeting, Conference
   This paper presented a site survey of an industrial site                            Paper no. C74 199-6, January, 1974.
                                                                                       Key, Thomas S., “Diagnosing Power-Quality Computer Problems”,
where the steady state rms voltage levels were non-compliant                           IEEE IAS Transactions, July/August, 1975, pp. 381-393.
for a significant portion of the time. A detailed analysis of                          Seebald, R. C., Buch, J. F., Ward, D. J., “Flicker Limitation of Electric
the survey results revealed that the high voltage conditions                           Utilities”, IEEE Transactions of Power Apparatus and Systems, Vol.
                                                                                       PAS-104, No. 9, Sept. 1985, pp. 2627-2631.
occurred during the night when the distribution feeder was                             Goldstein, M, Speranza, P. D., “The Quality of US. Commercial AC
lightly loaded and the low voltage conditions occurred during                          Power”, 1982 IEEE, CH 1818-41821/oooO-0028, pp. 28-33.
the day, during extremely heavy loading periods. Despite these                         Koval, D. 0..“How Long Should Power System Disturbance Site Mon-
                                                                                       itoring Be In Order to be Significant”, IEEE Transactions on Industry
extreme voltage variations, the industrial customer did not                            Application, July/August, 1990, Vol. 26, Number 4, pp. 556-562, pp.
complain about power quality.                                                          705-710.
                                                                                       Koval, D. O., “Power System Disturbance Patterns”, IEEE Transactions
   For each power quality site survey, a summary of the                                on Industry Applications, May/June, 1990, Vol. 26, Number 3, pp.
number of the various types of voltage disturbances that were                          556562.
captured during the monitoring period is prepared. A detailed                          Licsko, Z. L., Leonard, J. J., Koval, D.O., “Monitoring On-Farm
                                                                                       Electrical Power Quality in Alberta”, Paper No. 90-401, Canadian
mathematical model was presented for estimating the duration                           Society of Agricultural Engineering, Agricultural Institute of Canada
of voltage surges given only the energy content of the surge,                          Annual Conference, July 22-26, 1990, Penticton, British Columbia, pp.
the peak voltage level and an impedance provided by the                                1-23.
                                                                                       Koval, D. O., Report for the Canadian Electrical Association entitled:
power line monitor used in the power quality program. For                              State of the Art Study: SD-220, “Causes of Customer Power Supply
the other types of voltage disturbances, the monitor provided                          Disturbances and Their Effect on Customer Appliances”, CEA Research

HUGHES et al.: DISTRIBUTION CUSTOMER POWER QUALITY EXPERIENCE                                                                                           1211

     and Development, Suite 580, One Westmount Square, Montreal, Quebec                                     John S. Chan received the B.A.Sc. (Eng.) degree
     H3Z 2P9, Canada, March, 1987.                                                                          in 1961 from the University of Hong Kong.
~ 3 1CEA Report Number 400 U 495.: entitled “Type of Customer Problems                                         He joined BC Hydro in 1969 where he worked
     Caused by Momentary Interruptions”, CEA Research and Development,                                      most of his time in distribution engineering. He
     Suite 580, One Westmount Square, Montreal, Quebec H3Z 2P9, Canada,                                     was Distribution Engineering Manager for Lower
     March, 1987.                                                                                           Mainland Division from 1981 to 1988. Currently,
~ 4 Leonard, J. J., Cbang, J.. Licsko, 2. J., Report for the Canadian Electrical
     1                                                                                                      he is Manager, Revenue Metering Department. He is
     Association entitled. CEA Project 809 U 6 5 2 “Survey and Monitoring                                   also Project Manager for BC Hydro’s Power Quality
     of On-Farm Voltage Disturbances”, CEA Research and Development,                                        Survey and the Canadian Electrical Association’s
     Suite 580, One Westmount Square, Montreal, Quebec H3Z 2P9, Canada,                                     Canadian National Power Quality Survey.
     Februarv. 1990.                                                                                           Mr. Chan is a registered Professional Engineer
[15] Working Group 336.05 (disturbiang bads) C I G E , “Report on the              in the Province of British Columbia, Canada: He is also Chairman of the
     Results of the International Questionnaire COnWdng voltage Distur-            Canadian Electrical Association’s power Quality Workng Group.
     bances”, ELECTRA, W9, March, 1985, pp. 47-56.
[I61 Bonnard, G.,‘The Problems Posed by Electncal Supply to Industrial
     Installations”, IEEE Proceedings, Vol. 132, Pt.B, No. 6, November,
     1985, pp. 335-343.
[17] International Union of Producers and distributors of electrical Energy             0. Koval, photograph and biography not available at the time of
     UNPEDE: “Characteristics of the Electricty Supply voltage for Low             publication.
     Voltage Consumers”, Characteristiques de la tension, BT, PP. 613-622.

                         Brent M. Hughes received the B.A.Sc. in 1975 and
                         the M.A.Sc. in 1985 from the University of British
                         Columbia, Canada.
                            He joined BC Hydro’s System Engineering Divi-
                         sion in 1975, where he worked in the Analytical
                         Studies and Area Transmission Planning Depart-
                         ments. In 1989, he joined Powertech Labs Inc.
                         (formerly BC Hydro Research and Development) as
                         a Senior System Studies Engineer. He is currently
                         the principal investigator for BC Hydro’s Power
                         Quality Survey Program and the Canadian Electrical
Association’s National Power Quality Survey.
   Mr. Hughes is a member of E E E and a registered Professional Engineer
in the Province of British Columbia.

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