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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

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 ?

LOW POWER FACTOR

CAPACITOR

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

WAPDA                KWh KVARh                      CONSUMER

KW                        KW
KVAR

Power Factor Improvement
by Installation of Capacitor
10
CAPACITOR
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
associated equipment.
11
POWER FACTOR
3. Copper losses in transformers also increases.
4. Generators, transformers, switches, transmission
lines and other associated switchgear becomes
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   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:
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
FACTOR IMPROVEMENT
PFI Capacitor’s addition, thus can be viewed in two lights.

i. Adding capacitor, releases circuit capacity for
capacitor KVAR per KVA of load increase is of
particular interest as this establishes the average
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
FACTOR IMPROVEMENT
ii. Capacitors applied to given load reduce the I2R
losses in the supply circuit. For a 70 percent power
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
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
FACTOR IMPROVEMENT
3. Improves voltage level at the load.
5. Reduces investment in system facilities per
6. Eliminates low power factor penalty imposed
by WAPDA.

22
ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM
ROLE OF CAPACITOR IN DISTRIBUTION SYSTEM

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
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
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
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

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
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
Reduce Investment in System Facilities per KW of

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
KVAR                             KVAR
G/Station

Meters
After Installation of Capacitor              Kvarh
Kwh

KW                             KW
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.

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.
Assume 100 KVA Circuit or piece of apparatus has to carry 100 KVA at
various P.F.

60%        70%
140

130

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

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.

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.

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
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,

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
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
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
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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

80

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