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									 Power Distribution System

Power Factor Improvement
           BY
 INSTALLING CAPACITORS ON
   DISTRIBUTION SYSTEM




  Prof. Dr. Suhail Aftab Qureshi
                                   1
    WHAT IS POWER FACTOR?
Power Factor is the ratio of ACTIVE
POWER to the TOTAL POWER (apparent
power):

Power Factor =       Active Power                P
                                          =
                     Total Power                 S
S   =   Total power of Generator (or used)
P   =   Power consumed in the load (active power)
Q   =   Reactive power stored in magnetic field. Or
        wasted power
                                                      2
    WHAT IS POWER FACTOR?
Vectorial Representation:
                                       P
    S              P.Q             Φ    j=90o

                     Load                       Q
                                       S

Generator
       Total power = S = VI       = (units = KVA)
       Active power = P = VI CosΦ = (units = KW)
       Reactive power= Q = VI SinΦ = (units = KVAR)
V = Voltage : Volts                        V
I = Current : Ampere               Φ
Φ = Physical displacement of V&I
                                       I
Power Factor = CosΦ                             3
            WHAT IS LOW POWER
                FACTOR?
                         P
                  P.F. = S
 If the ratio of active power (P) to total power
 (S) is less than one (unity) then the power
 factor is low, which means total power is not
 being consumed.
 Example:
            S   = 100KVA                S   = 100KVA
            P   = 80KW                  P   = 100KW
Generator                   Generator
            P.F = 0.8                   P.F = 1.0
            Q   = 60-KVAR               Q =     0
                                                       4
WHAT IS LOW POWER FACTOR?

The above example clearly indicates that
a generator of total power of 100-KVA
will supply maximum of 80-KW of active
power to a load with P.F. = 0.8 and the
same generator will supply maximum of
100-KW of active power to load with
P.F = 1.0.

                                      5
      HOW TO IMPROVE THE
       POWER FACTOR ?
The power factor can be improved by
supplying KVAR to the loads (inductive type)

“Capacitor is source of KVARs”

Therefore the power factor of connected load
can be improved by installing power factor
improvement capacitors/capacitor banks
                                         6
        HOW TO IMPROVE THE
         POWER FACTOR ?

                LOAD
                LOAD
           LOW POWER FACTOR

              CAPACITOR


                LOAD
                LOAD
         IMPROVED POWER FACTOR
Fig.I                            7
            KVA AND KW SAVING




         COSΦ2 = 0.9
KVA (Saving) = S(KVA)1 – S(KVA)2

       Vectorial representation of P.F Improvement. 1&2
       refer to before and after improvement of P.F.

                                                          8
KVA AND KW SAVING




      COSΦ2 = 0.9
  KW (Saving) = P1 – P2   9
POWER FACTOR IMPROVEMENT
   BY CAPACITOR BANK
 WAPDA                KWh KVARh                      CONSUMER


             KW                        KW
            KVAR                      KVAR


                       METERS                          LOAD

 WAPDA                KWh KVARh                      CONSUMER


             KW                        KW
                                              KVAR


                       METERS                          LOAD

  Power Factor Improvement
  by Installation of Capacitor
                                                                10
                                  CAPACITOR
     DISADVATAGES OF LOW
        POWER FACTOR
• For a given power to be supplied, the current
  is increased.
• The current thus increased in-return causes
  increase in copper losses (PL=I2R) and
  decrease in the efficiency of both apparatus
  and the supply system, which results in
  overloading and hence burning of the
  associated equipment.
                                            11
      DISADVATAGES OF LOW
         POWER FACTOR
3. Copper losses in transformers also increases.
4. Generators, transformers, switches, transmission
   lines and other associated switchgear becomes
   over-loaded.
5. Voltage regulation of generators, transformers
   and transmission lines increases.
6. Hence, cost of generation, transmission and
   distribution increases.
                                                   12
    NATURAL POWER FACTORS
o   CEILING FAN            0.5 TO 0.7
o   CABIN FAN              0.5 TO 0.6
o   EXAUST FAN             0.6 TO 0.7
o   SEWING MACHINE         0.6 TO 0.7
o   WASHING MACHINE        0.6 TO 0.7
o   RADIO                  0.9
o   VACUUM CLEANER         0.6 TO 0.7
o   TUBE LIGHT             0.5 TO 0.9
o   CLOCK                  0.9
o   ELECTRONIC EQUIPMENT   0.4 TO 0.95
                                    13
    NATURAL POWER FACTORS
o   NEON SIGN                     0.5 TO 0.55
o   WINDOW TYPE AIR CONDITIONER   0.62 TO 0.85
o   HAIR DRYERS                   0.7 TO 0.8
o   LIQUIDISER                    0.8
o   MIXER                         0.8
o   COFFEE GRINDER                0.75
o   REFRIGERATOR                  0.65
o   FREEZER                       0.7
o   SHAVER                        0.6
o   TABLE FAN                     0.5 TO 0.6
                                           14
    NATURAL POWER FACTORS
o   MERCURY VAPOUR LAMP           O.4 TO 0.6
o   INDUSTRIAL INDUCTION MOTOR:
    ◘    NO LOAD                  O.18
    ◘    25% FULL LOAD            0.56
    ◘    75% FULL LOAD            0.81
    ◘    100% FULL LOAD           0.85
    ◘    125% FULL LOAD           0.86
o   COLD STORAGE                  O.76 TO 0.80
o   CINEMAS                       0.78 TO 0.80
o   METAL PRESSING                O.57 TO 0.72
                                           15
    NATURAL POWER FACTORS
o   OIL MILLS                    O.51 TO 0.59
o   WOOLEN MILLS                 O.70
o   POTTERIES                    0.61
o   CIGARETTE MANUFACTURING      0.80
o   FOUNDRIES                    0.59
o   STRUCTURAL ENGINEERING       0.53 TO 0.68
o   CHEMICALS                    0.72 TO 0.87
o   MUNICIPAL PUMPING STATIONS   0.65 TO 0.75
o   OIL TERMINALS                0.64 TO 0.83
o   ROLLING MILLS                0.60 TO 0.72
                                          16
    NATURAL POWER FACTORS
o   PLASTIC MOLDING               0.57 TO 0.73
o   FILM STUDIOS                  O.65 TO 0.74
o   HEAVY ENGINEERING WORK        0.48 TO 0.75
o   RUBBER EXTRUSION AND MOLDING 0.48
o   PHARMACEUTICALS               0.75 TO 0.86
o   OIL AND PAINT MANUFACTURING   0.51 TO 0.69
o   BISCUIT FACTORY                      0.60
o   LAUNDRIES                     0.92
o   FLOUR MILLS                   0.61
o   GLASS WORKS                   0.87
                                            17
    NATURAL POWER FACTORS
o   IRRIGATIONS PUMPS             O.62 TO 0.80
o   REPAIR SHOP, AUTOMATIC LATHE, 0.6
    WORKSHOP, SPINNING MILLS,
    WEAVING MILL
o   WELDING SHOP                  0.5 TO 0.6
o   HEAT TREATMENT SHOP, STEEL    0.65 TO 0.8
    WORKS, ROLLING MILLS
o   TEXTILE                       0.65 TO 0.75
o   CEMENT                        0.8 TO 0.85
o   OFFICE BUILDING               O.8 TO 0.85
                                           18
        ADVANTAGES OF POWER
         FACTOR IMPROVEMENT
PFI Capacitor’s addition, thus can be viewed in two lights.

   i. Adding capacitor, releases circuit capacity for
      more load or relieves the overloaded circuit. The
      capacitor KVAR per KVA of load increase is of
      particular interest as this establishes the average
      cost of supplying each additional KVA of load.
      This cost can be compared with the cost per KVA
      of increasing the transformer or supply circuit
      rating and would justify the application of
      capacitors.
                                                      19
     ADVANTAGES OF POWER
      FACTOR IMPROVEMENT
ii. Capacitors applied to given load reduce the I2R
    losses in the supply circuit. For a 70 percent power
    factor load with 40-KVAR of capacitors added for
    each 100 KVA of circuit capacity, the I2R loss will
    be 59% of its former value. The losses are not only
    reduced in the circuit in which the capacitors are
    applied but in all the circuit back to and including
    the source generator.

                                                     20
      ADVANTAGES OF POWER
       FACTOR IMPROVEMENT
Automatic Power Factor improvement capacitors or
capacitor banks applied on the load end of circuit,
with lagging power factor (more than 95% loads),
have particular effects, one or more of which may be
the reason for the application.

 • Improves the power factor at the source.
 • Reduces system losses as current in
   conductors decreases.
                                                 21
    ADVANTAGES OF POWER
     FACTOR IMPROVEMENT
3. Improves voltage level at the load.
4. Decreases KVA loading on the source.
5. Reduces investment in system facilities per
   KW of load supplied.
6. Eliminates low power factor penalty imposed
   by WAPDA.

                                                 22
ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM
ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM
 Disadvantages of Low Power Factors.

 The disadvantages of low power factor are summarized below:-

   In transmission/distribution lines, it is only in phase component of
   line current, which is active in the transmission of power. When P.F
   is low, then in phase (active) component is small but the reactive
   component is large, hence unnecessarily large current is required
   to transmit a given amount of power. Large reactive component
   means, large voltage drop, and hence greater Cu-losses with the
   results that regulation is increased and efficiency is decreased.

   Supply authorities usually bound to maintain the voltage at
   consumer’s terminal within prescribed limits, for which they have to
   incur additional capital cost of tap changing gear on transformers to
   compensate for the voltage drop. Hence the supply authorities
   penalize the industrial consumers for their low P.F by charging
   increased tariff for KVA maximum demand in addition to useful KW
   charge. Obviously it is advantageous for the consumer to improve
   his load P.F.                                                    23
ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM

 How to Improve the Power Factor.

   Power factor can be improved by supplying KVAR to the Inductive
   load. Different techniques to improve the P.F are given below:-

    §   With Synchronous Motors
    §   With Capacitors

   Synchronous  motors are not commonly used in distribution
   network for P.F improvement because it requires regular
   maintenance & also expensive. This method is mostly used to raise
   P.F of system having large Induction Motor loads. Also it is difficult
   to install at

   In distribution system, Capacitors are the most common method
   for power factor correction as it is the least expensive & almost
   maintenance free.
                                                                    24
ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM
ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM
 Power Factor Correction with Capacitors.

        Capacitor is a source of KVARs i.e it provides a static source of
        leading reactive current. It is desirable to add capacitors in the load
        areas supplying the lagging component of the current. There are two
        types of Capacitors according to their mode of installation.
  i.       Series Capacitors
  ii.      Shunt Capacitors
        Series  Capacitors have some draw backs because all load current
        will flow through capacitors, so if the load is more then we need big
        capacitor, further it boost the voltage at the point of installation.
        Shunt  Capacitors are more suitable for installation on distribution
        feeder as it produce a uniform voltage boost per unit of length of line,
        out of its point of installation. Therefore, it should be installed as far
        out on distribution system as practical, close to the loads requiring the
        KVARs.Shunt Capacitor can be viewed in two lights. Adding
        Capacitors releases circuit capacity for more load, and adding
        capacitors relieve over loaded circuits.
                                                                           25
ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM
ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM
Power Factor Correction with Capacitors.
    There are two types of Shunt Capacitors.

     i.Switched Capacitors
     ii.Fixed Capacitors


Switched Capacitor

    Switched Capacitors banks are programmable capacitors & can be
    switched on/off during load cycles by different program
    settings.Time Clocks, temperature, voltage, current and kilovars
    controls are common actuators for capacitor switching.

    Switched Capacitors are usually applied to correct the power factor
    to 0.97 at peak load (if economical). Each Switched Capacitor bank
    should save at least 8 KW loss at peak load.

                                                                  26
ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM

 Power Factor Correction with Capacitors.

 Fixed Capacitors
   Fixed Capacitor bank are usually applied to correct the power factor
   to unity at light load (if economical) & permanently connected into
   the system through fuses.

   Proposed permanently connected capacitor application should be
   checked to make sure that the voltage to some consumers will not
   rise too high during light load periods.

   Each Fixed capacitor bank should save at least 1 KW loss at light
   load.

   These are quite cheap as compared to switched capacitors,
   therefore, they are often used in distribution network to improve the
   power factor.                                                     27
ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM
ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM

  Benefits to Be Achieved by Installing
  Shunt Capacitors on Power Distribution
  System.
  Reactive Power Compensation i.e decrease KVA
  loading on source, therefore, additional KW
  loading may be placed without augmenting the
  existing system.
  Power Factor Improvement
  Reduction in Line Current i.e reduce lagging
  component of circuit current.
  Reduction in System Losses i.e reduce I2 R power
  loss & I2X Kilovar losses in the system.      28
ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM
ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM

Benefits to Be Achieved by Installing Shunt
 Capacitors on Power Distribution System.
 Reduction in Voltage Drop i.e increase voltage level
 at the load.
 Reduce Investment in System Facilities per KW of
 Load Supplied.

 Advantage No.1 is a direct consequence of installing
 a shunt capacitor because the same supplies the
 reactive demand to the load, relieving extra burden
 to reactive power. Thus due to reactive power
 compensation all other advantages are automatically
 achieved.                                      29
ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM
ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM
Power Factor Improvement By Capacitor Bank
 Before Installation of Capacitor     Meters
                                    Kwh      Kvarh

                      KW                              KW
                                                                    Load
                    KVAR                             KVAR
      G/Station

                                         Meters
 After Installation of Capacitor              Kvarh
                                     Kwh

                        KW                             KW
                                                                       Load
                        KVAR
        G/Station
                                                      KW        KVAR

                                                        Capacitor          30
ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM
ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM
     Some Examples which Illustrate the Benefits to be Achieved By
     Installing Capacitors.

i.   Reactive Power Compensation i.e Decrease in KVA Loading at
     Source.
     Assume that a single phase load supplied from a single phase A.C
     System with supply voltage as 230 Volts has active & reactive power
     demand as 3000 Watts and 4000 Vars respectively. If we install a
     shunt capacitors of rating 3000 Vars on the load point, then reactive
     power equal to 3000 Vars is compensated and directly supplied by the
     capacitor, leaving behind only 1000 Vars on the system. The Effect is
     shown by the following calculations.

     VA burden on the System before installation of Capacitors =
     ( 3000² + 4000²)1/2 = 5000 VA
     VA burden on the System after installation of Capacitors =
     (3000² + 1000²)1/2 = 3162 VA
     It means that VA burden on the system has been largely reduced due
                                                                  31
     to reactive power compensation.
 ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM
ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM
        Some Examples which Illustrate the Benefits to be Achieved By
        Installing Capacitors.
 i.     Reactive Power Compensation i.e Decrease in KVA Loading at Source.
       Assume 100 KVA Circuit or piece of apparatus has to carry 100 KVA at
       various P.F.


                                                   60%        70%
                   140
      % Load KVA

                   130




                                                              80% Load P.F
                   120




                                             90%
                   110
                    100
                   150




                         0   20         40               60      80          100
                                  CAP. Kvar in % of Circuit KVA                    32
      ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM
          Some Examples Illustrating the Benefits to be Achieved By Installing
          Capacitors.

ii.       Power Factor Improvement

          This advantage is obtained as a consequence of reactive power
          compensation.
          From the example discussed in (i) above we can conclude as under:-

      §      Power Factor before installation of a shunt capacitor = W = 3000 = 0.6
                                                                   VA 5000

      §      Power Factor after installation of a shunt capacitor = W = 3000 = 0.949
                                                                    VA1 3162

          It means power factor has been improved from 0.6 to 0.949.

                                                                                  33
 ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM
ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM
      Some Examples which Illustrate the Benefits to be Achieved By
      Installing Capacitors.
ii.   Power Factor Improvement.
      Assume 100 KVA Circuit or piece of apparatus has to carry 100 KVA at
      various P.F.
                    100
       Circuit P. F %




                                 90%     80%          70%
                        90




                                                            60% Load P.F
                        80
                        70




                             0     20          40        60           80   100
                        60




                                        CAP. Kvar in % of Circuit KVA
                                                                                 34
ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM
ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM

           Some Examples Illustrating the Benefits to be
           Achieved By Installing Capacitors.
iii.       Reduction in Line Current
           As the reactive power compensation causes reduction in VA burden
           of the line, so for a system having regulated supply voltage, it can be
           seen that reactive compensation actually causes reduction in line
           current.
           From the data of (i) the values can be calculated as under:-
       §      VA before installing capacitor was = 5000, V = 230 Volts

       §      VA = V x I,       Therefore I = (VA/V) = (5000/230) = 21.7 Amps

       §      VA after installing capacitor was = 3162,          V = 230 Volts

       §      VA1 = V x I1      Therefore I1 = (VA1/V) = (3162/230) = 13.7 Amps

           It means that current has been reduced from 21.7 Amps to 13.7
           Amps.                                                   35
      ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM
      ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM
          Some Examples Illustrating the Benefits to be
          Achieved By Installing Capacitors.
iv.       Reduction of System Losses
          Assume that power was supplied through 800 ft. long S/Phase L.T line
          of Gnat conductor having resistance per mile as 2.11 ohms and
          capacitor has been installed. The losses can be calculated as under:-
      §      Resistance R = (2.11 x 800)/5280 = 0.32 ohms      [ 1 mile = 5280 ft.]

      §      System Losses for one year = 2 (VA)² x0.32 x8760 =2 (5000)²x 0.32 x
             8760
             without Capacitor                (V)²                (230)²
                                                            = 2649527 Watt hours
      §      System Losses for one year with capacitor
      §      =2(3162)²x0.32x8760/(230X230)=

      §                              1059625 Watt hours
      §      %age Reduction in System Losses = (2649527
                                                    36
             – 1059625 )x 100/2649527 = 60%
ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM
         Some Examples Illustrating the Benefits to be Achieved By
         Installing Capacitors.
v.       Reduction in Voltage Drop
         Voltage Drop before and after installing shunt capacitor can be calculated by
         using the following formulas.
     §      V.D = (R x W) + (Xl x VAR) OR       V.D = Ir R + Ix X   Without Capacitor
                          V
     §      V.D = (R x W) + (Xl x VAR1) OR      V.D = Ir R + Ix X – IcX With Capacitor
                          V
         Suppose
         R = 0.64 ohm for S/P circuit Xl = 0.145 ohm for S/P circuit, V = 230 Volts
         W = 3000 Watt,              VAR = 4000 Vars,               VAR1=1000 Vars

     §      V.D = (0.64 x 3000) + (0.145 x 4000) = 10.86            Volts Without Capacitor
                               230
     §      V.D = (0.64 x 3000) + (0.145 x 1000) = 8.97 Volts           With Capacitor
                             230
         Reduction in Voltage Drop = 10.86 – 8.97 = 1.89 Volts
                                                                                         37
   ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM
        Vectorial Representation of Power Factor
          Improvement                P (KW)
After improving P.F from ø1 to ø2,                  ø2
KVAR is reduced from Q1 to Q2. The             ø1
difference in values of KVAR is due                                 S2              Q2 (KVAR)
to capacitor, which supply leading                                 (KV
                                                                       A)
KVAR (Qc) to partially neutralize the                    S1
lagging KVAR of the System.                                   (K                            Q1 (KVAR)
                                                                VA
                                                                   )
                                                                                    Qc (KVAR)
  Leading KVAR Supplied by Capacitor is Qc = Q1 – Q2
                                               Qc = P (tan ø1 – tan ø2)

      Before Capacitor Installation                       After Capacitor Installation
      ø1= Power Factor before Improvement                 ø2= Power Factor After Improvement
      P = Active Power (KW) at ø1                         P = Active Power (KW) at ø2
      S1 = Apparent Power (KVA) at P.F ø1                 S2 = Apparent Power (KVA) at P.F ø2
      Q1= Reactive Power (KVAR) at at P.F ø1              Q2= Reactive Power (KVAR) at at P.F ø2
                                                                                               38
ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM
ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM
 Effect of Shunt Capacitors on Feeder Voltage Profile 
       The effect of shunt capacitor application on voltage profile of
       Feeder, where the load is assumed to be uniformly distributed
       along the Feeder is illustrated in figure as below.

                            Uniformly distributed Load
   Sub Station
                                                            Capacitor
                                                                        Rise produced
                                                                        by Capacitor

          Volts
                                                Reference                Feeder Profile
                                                                         with Capacitor

                                                                         Feeder Profile
                                                                        without Capacitor
            Sub Station             Distance


          Voltage Profile of Feeder With & Without Capacitor
                                                                               39
ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM
  Effect of Shunt Capacitors on Feeder Voltage Profile

     §   Capacitors produces a voltage rise because of its leading
         picofarad current flowing through the inductive reactance of
         the feeder.

     §   As is seen in the figure, this voltage rise increases linearly
         from zero at sub station to its maximum value at the
         capacitor location.

     §   Between the capacitor location & the remote end of the
         feeder, the rise due to capacitor is at its maximum value.

     §   When the capacitor voltage-rise profile is combined with
         original feeder profile, the resulting net profile is obtained.

     §   The capacitor has increased the voltage level all along the
         feeder, resulting also in reduced voltage spread..      40
ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM
ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM

  Effect of Shunt Capacitors on Feeder
  Voltage Profile

  Proposed permanently connected capacitors
  should be checked to make sure that voltage to
  some customers will rise too high during light load
  periods.

  Switched capacitor application should be checked
  to determine that switching the capacitor bank on
  or off will not cause objectionable voltage flicker.

                                                  41
ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM
ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM
    Effect of Series Capacitor on Feeder Voltage Profile
      The effect of series capacitor application on voltage profile of
      Feeder, where the load is assumed to be uniformly distributed along
      the Feeder is illustrated in figure as below.

                           Uniformly distributed Load
    Sub Station
                                                               Series Capacitor

                                                                             Rise produced
                                                                             by Series Cap

           Volts
                                                   Reference                  Feeder Profile
                                                                              with series Cap

                                                                              Feeder Profile
                                                                            without Series Cap
             Sub Station               Distance

•   The series capacitor produces no voltage effect between the source & the
    capacitor location and its entire boost effect is between the capacitor location
    and the remote end of the feeder.                                         42
ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM

Effect of Voltage Regulator on Feeder Voltage Profile
     The effect of feeder voltage regulator is shown in figure below
                             Uniformly distributed Load
      Sub Station
                                                                 Voltage Regulator

                                                                               Rise produced
                                                                                by regulator

             Volts
                                                     Reference                  Feeder Profile
                                                                                with regulator

                                                                                Feeder Profile
                                                                               without regulator
               Sub Station               Distance


 •    Like series capacitor, voltage regulator produces no voltage effect between the
      source & the regulator location and its entire boost effect is between the
      regulator location and the remote end of the feeder.                     43
ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM
ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM
 Common Methods of Connecting Capacitors

 Most common methods of connecting capacitors are as under:-

   3-Phase Grounded Wye

   3-Phase Ungrounded Wye

   3-Phase Delta

   Single Phase




                                                               44
  ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM
   Common Methods for Connecting Capacitors




Fuse


                      Gnd


                                                                   S/P Ground to
                            Ungrounded wye          Delta             Neutral
       Grounded wye

         Grounded Wye & Ungrounded Wye connections are usually made
         on high voltage circuits, whereas delta & single phase connections
         are usually made on low voltage circuits.

         Majority of Capacitor equipment installed on distribution feeders is
         connected grounded wye.
                                                                         45
ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM
 Common Methods for Connecting Capacitors
   Grounded wye connection has number of advantages & benefits 
   over Ungrounded wye connection.

   With grounded wye connection, capacitor tanks/frames are at ground
   potential. This provides increased personnel safety.

   Grounded wye connections provides for faster operation of the series
   fuse in case of a capacitor failure.

   Grounded capacitors can bypass some line surges to ground and
   therefore exhibit a certain degree of self-protection from transient
   voltages & lightning surges.

   The grounded wye connection also provides a low impedance path
   for harmonics.
                                                                 46
ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM

  Common Methods for Connecting Capacitors

    If the capacitors are electrically connected ungrounded wye, the
    maximum fault current would be limited to three times line
    current. If too much fault is available, generally 5000 A, the use of
    current limiting fuses must be considered.




                                                                      47
ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM
ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM

How Many Capacitors to Install

  The number of capacitors to install to raise the power factor
  from one value to another can be computed by using Stander
  Table.




                                                                  48
ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM
    ROLE OF CAPACITOR IN DISTRIBUTION 
                SYSTEM
 How Many Capacitors to Install




                                         49
  ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM
  ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM
How Many Capacitors to Install




                                       50
ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM
How to Select a Location Of Capacitor to be Installed

  The application of shunt capacitor to a distribution feeder produces a
  uniform voltage boost per unit length of line, out to its point of
  application. Therefore it should be installed as far out on distribution
  system as practical, close to load requiring the Kvars.

  Many Factors influence the location of Capacitor such as the circuits in
  plant, the length of the circuits, the variation in load, the load factor,
  type of motors, distribution of loads, constancy of load distribution.

  The maximum loss reduction on a feeder with distributed load is
  obtained by locating capacitor banks on the feeder where the
  capacitor kilovars is equal to twice the load kilovars. This principle
  holds whether one or more than one capacitor bank is applied to a
  feeder.
                                                                      51
ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM

  Protection Principles
  There are several major factors which must be considered during
  the design phase of a power factor correction capacitor
  application.
    i.   Fundamental Protection Principles

    §    Safety of all personal who are required to work near or with
         the equipment should be of prime importance.
    §    Capacitors should be connected to system through fuses
         so that a capacitor failure will not jeopardize system
         reliability or result in violent case rupture.
    §    To assure that the proper fuse protection is provided, the
         installed capacitor fuse ratings are listed in standard
         Tables.


                                                                   52
ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM
ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM
 Protection Principles
    ii.   Capacitor Tank Rupture

    •     Capacitor tank rupture will occur if the total energy applied to
          capacitor under failure conditions is greater than the ability of
          the capacitor tank to withstand such energy.

    •     Tank rupture curves are essential for correct selection of fuse
          link for over current protection of any capacitor installation.

    •     Fuse selection should be based upon the coordination of the
          fuse link maximum clearing curve and the high voltage
          capacitor tank rupture curve


                                                                      53
ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM
Protection Principles
   iii.   Ventilation
   •      Although very efficient power capacitors do consume power and
          generate heat. This heat must be adequately ventilated when
          enclosed or exposed to higher than normal ambient
          temperature.
   iv.    System Voltage
   •      Capacitors are designed for operation on 50 or 60 Hz sine wave
          power lines at a specific voltage, which is mentioned on the unit
          name plate.
   •      However, they are normally designed to operate at over
          voltages of 10% without damage to the capacitor. The Kvar
          output of the capacitor increases as square of the applied
          voltage.
                         KvarE2 = Kvar (E2)²
                                         (E1)²
                                                                      54
ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM
ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM
 Protection Principles

    iv.   System Voltage

    §     For example 450 Kvar, 11 KV capacitor will supply 492 Kvar at 11.5
          KV.


                          KvarE2    =
                                        450 (11500)²
                                             (11000)²

                          KvarE2    =
                                        492



                                                                         55
ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM
 Protection Principles
    v.   Harmonics Distortion

    •    Capacitors are designed to operate on sine wave current with
         limited amount of harmonics.
    •    Typical applications that may cause harmonics current
         problems are arc furnaces, saturable reactors, rectifies and
         solid state motor controls.

    •    Capacitors are usually designed to operate 135% of rated
         Kvar. This includes any increase due to over voltage as well
         as that due to harmonic currents.
    •    The total rrms current equal to   (I60)2 + (I2)2 + (I3)2 + ------+
         (In)2
         where n = harmonic number


                                                                       56
ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM
Protection Principles

   vi.    Discharge Resistor
   •      When the line voltage is removed from a power capacitor, the
          danger exists that, even days later, under certain conditions, the
          unit would retain extremely high charge.
   •      To eliminate this hazard, all power capacitors contain internal
          discharge resistors. This resistor assembly will reduce the
          terminal voltage from line voltage to 50 V within 5 minutes of de-
          energization for capacitor rated higher than 1200 V ac and within
          1 minute for capacitors rated less than 1200 V ac.

   vii.   High Frequency Charging Current

   •      High frequency charging currents can result in blown fuses.
   •      The use of series reactors & special switches are sometimes
          required to reduce these currents to safe levels.
   •      Proper installation of lightening arresters will ensure the
                                                                   57
          protection of capacitor equipment from lightning surges.
ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM
 ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM
Example of Capacitor Applications on 11 KV Feeder
       11 KV Ex-Quality Feeder
       Before Installing Capacitor                   After Installing Capacitor
       • Peak Current = 198 Amps                     • Peak Current = 188.9 Amps
       • Power Loss = 99.6 KW                        • Power Loss = 87.4 KW
       • A.E.L          = 376752 KW                  • A.E.L           = 330852 KW
       • %Power Loss = 3%                            • %Power Loss = 3%
       • %A.E.L         = 2%                         • %A.E.L          = 2%
       • % V.D          = 6.1%                       • % V.D           = 4.9%

Benefits Achieved
• Current has been reduced from 198 to 188.9 Amps.
• Power loss has been reduced from 99.6 to 87.4 KW with Net Savings are 12.2 KW.
• A.E.L has been reduced from 376752 to 330852 KWH with Net Annual Savings are 45900 KWH.
• % V.D has been reduced from 6.1% to 4.9%
                                                                                      58
 ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM
 ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM
      Why the Line Staff is reluctant to put the capacitor in
      Circuit.


    It has been experienced that on tripping of the feeder, the
    man at the Grid Station tries to get the feeder
    held/energized without getting the capacitor discharged
    fully, the result of which is that the feeder does not hold.
    The line staff is also not bothered about the discharge of
    capacitor as well as solid earthing of the capacitor. The
    residual charge at the capacitor point do not allow the
    feeder to hold and thus the line staff always disconnect the
    capacitor in the first instance and then forget to get intact
    into the circuit.
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ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM

  11 KV CAPACITOR JUDGEMENT FACTORS
       (Minimum kW Saving)
       The following are the judgment factors in terms of kW saving accrued
       from the application of capacitors which indicate their feasibility.


 Capacitors                Rural                       Urban 
 Fixed Capacitors                (Saving at Off-Peak)
                                        
 450 KVAR                           1.2 KW                     1.2 KW
 950 KVAR                          1.6 KW                     1.6 KW 
 Switched Capacitors            (Saving at Peak) 
                                        
 450 KVAR                           8.7 KW                     4.9 KW
 950 KVAR                    10.4 to 11  KW                5.6 to 6 KW 
                                                                              60
ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM


 11 KV CAPACITOR JUDGEMENT FACTORS


Size of the fixed capacitor, to be installed on a feeder, should
be estimated at off peak load.

If off peak load of the feeder is not available, then 1/3rd of
the peak load may be taken for calculation purposes.

Size of the switched capacitor, to be installed on a feeder,
should be estimated at peak load of the feeder.




                                                                 61
          WAPDA CASE
   (STUDY PERFORMED BY KEL)
§ Practical demonstration was performed in presence of
  Chief Engineer ELR (Energy Loss Reduction), and
  Managing Director Power, WAPDA.
§ Sites selected:
   § 3-locations at Shalimar Grid Station
   § Average release in (KVA)               =   18%
   § Average release in capacity (KW)       =   23%

                                        CONTINUED   62
          WAPDA CASE
   (STUDY PERFORMED BY KEL)

§ Results were then presented, in a presentation,
  to the Chairman WAPDA in the presence of
  Member Power, Member Finance, number of
  G.M’s and Chief Engineers.

§ The Demonstration was appreciated.


                                   CONTINUED   63
          WAPDA CASE
   (STUDY PERFORMED BY KEL)
§ As a test case Garden Town Grid Station was
  assigned for feasibility study. The following were
  the results:

  § Net saving claimed by KEL      = 3.2 MW
  § Approximate pay back period    = 16/17 Months
  § Net saving to WAPDA in 3 years = Rs. 1,11,73,000.00


                                                    64
              AEB - MULTAN
Tariff    KVA  KVAR  Investment Penalty       Payable 
         Saving Reqd.           Charged        Period 
                                              (Month)
B-2      161527 211752   63527100   8962835                7
B-3      45365   60779   18233700   1632199               11
B-4      -      -           -         -          -
C-1(a)   -      -           -         -          -
C-1(b)  6358   7629       2288700   138128                17
C-2(a)   -      -           -         -          -
C-2(c)  2073   4224       1267200   208163                 6
Total 215323 284384      85316700 10941325                 8
                                                     65
                MULTAN REGION
   Study Peformed By WAPDA AEB Multan (Year 1990-91)


— KVA savings                :     2,15,323
— KVAR required              :     2,84,384
— Investment                 :     Rs. 8,53,16,700.00
— Penalty charged            :     Rs. 1,09,41,325.00
— Pay back period            :     8 months
  (only based on penalty)

                                                   66
         AEB - FAISALABAD
                                              Payable 
          KVA  KVAR             Penalty 
Tariff               Investment                Period 
         Saving Reqd            Charged
                                              (Month)
B-2      80718   99929   29978700   6995970      2
B-3      25869   30812    9243600    766316     12
B-4       1796   4116     1234800      4704     263
C-1(a)     -      -         -          -         -
C-1(b)      915  1591       47730     85152      6
C-2(a)       09    139      41700     13283      3
C-2(c)    4983   8014     2404200    056043      4
Total   114350 144601    43380300   8521468      5
                                                  67
            FAISALABAD REGION
  Study Peformed By WAPDA AEB Faisalabad (Year 1990-91)


— KVA savings                 :     1,14,350
— KVAR required               :     1,44,601
— Investment                  :     Rs. 4,33,80,300.00
— Penalty charged             :     Rs. 85,21,468.00
— Pay back period             :     5 months
  (only based on penalty)

                                                       68
       ENERCON STUDY
ENERCON (National Energy Conservation Center) piloted the idea of
energy conservation and system capacity release through power factor
improvement of industry in Pakistan. The estimate made by ENERCON,
projected that power factor improvement at 2400 industrial units had the
potential of relieving around 76 MW of system capacity.




                                                                   69
  PENALTY FOR LOW POWER FACTOR
Average Power Factor of a consumer at the point of supply shall not be
less than 90 percent. In the event of the said power factor falling below 90
percent, the consumer shall pay a penalty of two percent increase in the
fixed charges corresponding to one percent decrease in the power factor
below 90 percent. The fixed charges for the purpose of calculating the
penalty for low power factor shall, however, be determined with reference
to maximum demand during the month.

“ Power Factor “ means the ratio expressed as a percentage of the kilowatt
-hours to the kilovolt ampere- hours consumed during the month. In case
of those connections where KVAh meters do not exist and KVARh meters
are installed, Power Factor shall be the ratio of KWh to square root of sum
of square of KWh and KVARh, i.e.
                                                        -1
P.F.= KWh        =     KWh                    = Cos (Tan KVARh )
       KVAh            (KWh)2+ (KVARh)2                     KWh
                                                                       70
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72
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74
75
76
77
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                      SCHWABE

                 Inductance: 0.756


Without Capacitor           W/Capacitor 3.5 uF + - 5%

Voltage : 225 VAC               Voltage : 225 VAC
 Ampere: 365 mA                 Ampere : 217 mA
  Wattage: 46 W                  Wattage : 46 W
Power Factor : 0.57             Power Factor 0.95




                                                        79
                      HELVAR
                 Inductance: 0.91 H

Without Capacitor           W/Capacitor 3.5 uF + - 5%

Voltage : 225 VAC               Voltage : 225 VAC
 Ampere: 352 mA                 Ampere : 208 mA
  Wattage: 44 W                  Wattage : 44 W
Power Factor : 0.56             Power Factor 0.95




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