The document discusses electrical power supply systems and power factor correction. It provides details on components of an electric power supply system including power stations, transmission lines, and distribution. It defines power factor and different types of electrical power. The document also discusses causes of low power factor, various power factor improvement equipment like static capacitors, synchronous condensers and phase advancers. It provides advantages and disadvantages of these equipment. Finally, it discusses effects of improving power factor such as reduction in transformer rating, KVAR demand, line current, line losses, cable size and switchgear rating.

1. Electrical Power Supply System
The conveyance of electric power
from a power station to consumer,s
premises is known as electrical
Power supply system.
An electric supply system consists of three principal components .
1-Power Station
2-Transmission lines
3-Distribution

3. Power factor
The cosine of angle between voltage
and current in ac circuit is known as
power factor.
Power factor (Cos )= KW/KVA

4. Electrical Power
1. Active Power (kw = kva cos ( 3 V I Cos )
2. Reactive Power (kvar = kva sin
3. Apparent Power (kva = (kw2+kvar2)
KVA
KW
KVAR

5. Types Of Loads
1-Incandescent Lamp 0.98-1.0
2-Flourescent Lamp 0.6-0.8
3-Neon Lamp used for advertisement 0.4-0.5
4-Arc lamps used in cienema 0.3-0.7
5-Fans 0.5-0.8
6-Induction Heaters 0.85
7-Resistance Furnaces 0.6-0.9
8-Arc Furnaces 0.85
9-Induction Furnaces 0.6
10-Arc welders 0.3-0.4
11-Resistances Welders 0.65
12-Induction Motors 0.5-0.85
13-Fractional h.p.motors 0.4-0.75
Effect of low Power Factor
Heat = I*2 R T
I ά to 1/ cosø
H ά (1/ cosø)*2
A low P.F. would mean increased heat losses.

6. Causes of Low Power factor
1.Induction Motors
2.Arc Lamps, electrical discharge Lamps
3.Industrial Heating furnace at low lagging
power factor
4.From power system.

7. Power factor Improvement
Equipment
1.Static capacitor
Advantage-
1.They have low losses
2.They require little maintenance as there are no rotating parts
3.They can be easily installed as they are light and require no foundation
4.They can work under ordinary atmospheric conditions
Disadvantages
1.They have short services life ranging from 8 to 10 years.
2.They are easily damaged if the voltage exceeds the rated value.
3. Once the capacitors are damaged, there repair is uneconomical.

8. Static Capacitor

9. Asynchronous motor takes a leading current when over excited and
,therefore,they acts as a capacitor.An overexcited synchronous motor running
on no load is known as synchronous condensor.
Advantage-
1.By varying the field excitation ,the magnitude of current drawn by
motor can be changed by any amount.this helps in achieving step less
control of power factor.
2.The motor winding have high thermal stability to short circuit currents
3.The faults can be removed easily
Disadvantages
1.There are considerable losses in the motor.
2.The maintenance cost is high.
3.It produces noise .
4.Except in sizes above 500kva ,the cost is greater than that of static
capacitors of the same ratings.
5.As a synchronous motor has no self starting torque,therefore,an
auxiliary equipment has to be provided for this purpose
Synchronus Condensor

10. Synchronous Condenser

11. Phase advancer is a simple AC exciter which is connected on the main shaft of the
motor and operates with the motor’s rotor circuit for power factor improvement. Phase
advancer is used to improve the power factor of induction motor in industries.
As the stator windings of induction motor takes lagging current 90° out of phase with
Voltage, therefore the power factor of induction motor is low. If the exciting ampere-
turns are excited by external AC source, then there would be no effect of exciting
current on stator windings. Therefore, the power factor of induction motor will be
improved. This process is done by Phase advancer.
Advantages:
1-Lagging kVAR (Reactive component of Power or reactive power) drawn by the motor
is sufficiently reduced because the exciting ampere turns are supplied at slip frequency
(fs).
2-The phase advancer can be easily used where the use of synchronous motors is
Unacceptable
Disadvantage:
1-Using Phase advancer is not economical for motors below 200 H.P. (About 150 KW)
Phase advancer

12. Phase Advancer

13. Reduction in
Transformer Rating
Reduction in KVAR
Demand
Advantages of P.F
Correction
Reduction in KVA
Demand
Reduction in Line
Current
Reduction in Line
loss
Reduction in
Cable / Bus-bar
size
Reduction in
Switchgear
Rating

14. REDUCTION IN KVA DEMAND
LOAD - 900 KW
EXISTING P.F. (COS - 0.6
DESIRED P.F. (COS ) - 0.92
KW
Ø.
KVA 1 = 900 / 0.6 = 1500
KVA2 = 900 / 0.92 = 978
Ø 1)
Ø2
kW
kVA
COS =
KVA =
Ø.
kW
cosØ.
Reduction in KVA
1500 - 978 = 522

15. REDUCTION IN KVAR
DEMAND
kVA =
KVAR1 =
=
KVAR 2 =
KW2 + KVAR2
KVA1
2 - KW2
1500 2 - 900 2 = 1200
978 2 - 900 2 = 382
KW - 900
KVA1 - 1500
KVA2 - 978
KW
Ø.
KVAR
Reduction in KVAR
1200 - 382 = 818

16. REDUCTION IN LINE
CURRENT
KVA =
I =
I1 =
=
I2 =
=
3 V I
1000
KVA x 1000
3 x 415
1500 x 1000
3 x 415
2087 Amp
978 x 1000
3 x 415
1361 Amp
KVA1 - 1500
KVA2 - 978
Reduction in Current
2087 - 1361 = 726

17. 0
10
20
30
40
50
60
70
80
90
100
1 0.9 0.8 0.7 0.6 0.5
% Rise in Current w.r.t.
decrease in Power Factor
% Rise in I n
P.F.

18. % of saving in losses = 1-
Cos
Cos
Ø1
Ø2
2
1-
0.6
0.92
2
X 100
X 100
= 57.46
Cable Losses

19. 0
10
20
30
40
50
60
70
80
0.5 0.6 0.7 0.8 0.9 1
Saving in Cable Losses
P.F.
1.0
0.95
0.9
0.85
0.8
Initial P.F.

20. Saving in losses = Wr x K1
Wr = Full load copper loss of the transformer
connected load in Kw
k1
KVA rating of the transformer
1
CosØ1
1
CosØ2
-
Transformer Losses

21. Graph Transformer Losses

22. Transformer Losses
0
5000
10000
15000
20000
25000
30000
35000
40000
0 500 1000 1500 2000 2500 3000 3500
Transformer KVA
cu
Loss
Copper losses

23. Transformer Losses
Saving in losses = Wr x K1
1
CosØ1
1
CosØ2
-
=
900
1500
1 1
0.6 0.92
= 6260 Watts
Annual Saving = 6260 x 300 x 12
1000
= 22536 KWH
18000 x x

24. Power Savings
KVA X'MER CURRENT ACB
RAT I NG
1500
978
1500
1000
2086
1360
2500
0
500
1000
1500
2000
2500
3000
KVA X'MER CURRENT ACB
AT 0.6 PF AT 0.92 PF
1600

25. What are the effects of harmonics on motor operation
and performance?
Harmonics increase motor losses, and can adversely affect the operation of
sensitive auxiliary equipment. The non-sinusoidal supply results in
harmonic currents in the stator which increases the total current drawn. In
addition, the rotor resistance (or more precisely, impedance) increases
significantly at harmonic frequencies, leading to less efficient operation.
Also, stray load losses can increase significantly at harmonic frequencies.
Overall motor losses increase by about 20% with a six-step voltage
waveform compared to operation with a sinusoidal supply. In some cases
the motor may have to be de-rated as a result of the losses. Alternatively,
additional circuitry and switching devices can be employed to minimize
losses.
Instability can also occur due to the interaction between the motor and the
converter. This is especially true of motors of low rating, which have low
inertia. Harmonics can also contribute to low power factor.

26. Correction of Poor power factor
Write some strategies for correcting poor power factor in motors?
The following are strategies for correcting power factor in motors:
1. Minimise operation of idling or lightly loaded motors
2. Ensuring correct supply of rated voltage and phase balance
3. Installing capacitors to decrease reactive power loads

27. Capacitor rating
The size of capacitor required for a particular motor depends upon
the no-load reactive kVA (kVAR) drawn by the motor, which can be
determined only from no-load testing of the motor. In general, for
full loading operating motor, the capacitor selected to not exceed
90 % of the no-load
kVAR of the motor. (Higher capacities could result in over-voltages
and motor burn-outs).
What is the thumb rule for installing capacitors to motor
terminal?
The size of capacitor required for a particular motor depends upon
the no-load reactive kVA (kVAR) drawn by the motor, which can be
determined only from no-load testing of the motor. In general, the
capacitor is then selected to not exceed 90 % of the no-load kVAR
of the motor. (Higher capacities could result in over-voltages and
motor burn-outs). Alternatively, typical power factors of standard
motors can provide the basis for conservative estimates of capacitor
ratings to use for different size motors.

28. Star Connected motors
Why is it beneficial to operate motors in star mode for under loaded
motors?
For motors which consistently operate at loads below 50 % of
rated capacity, an inexpensive and effective measure might be to
operate in star mode. A change from the standard delta operation
to star operation involves re-configuring the wiring of the three
phases of power input at the terminal box.
Operating in the star mode leads to a voltage reduction by a factor of
‘square root of 3’. Motor output falls to one-third of the value in the
delta mode, but performance characteristics as a function of load remain
unchanged. Thus, full-load operation in star mode gives higher efficiency
and power factor than partial load operation in the delta mode. However,
motor operation in the star mode is possible only for applications where
the torque-to-speed requirement is lower at reduced load.

29. Efficiency Of Electricity
Name the two important parameters that attribute to efficiency of
electricity use by AC induction Motors?
The important parameters that attribute to efficiency of electricity use by
AC induction Motors are
1. Efficiency of the motor
2. Power Factor

30. Measurements of Capacitor KVAR Ratings
MCC Details
Before Power Factor Improvement
After Power Factor
Improvement
Location
Line
Voltag
e VL Line Current IL
Reactive power
KVAr
Apparent
Power KVA
Active
Power KW
Cos #
P.F.
Multipling
Factor
Required
Kvar
KVA
Requiremen
t
Load
Current
Reduction In
KVA
Demand
Reduction
In current
% Saving
In Cable
Losses
Budgetry Cost of APFC
Panel alongwith Reactors
Paste Plant 415.00 152.00 60.00 84.00 69.00 0.75 0.74 51.02 69.70 96.97 14.30 55.03 42.61 112244.69
Paste Plant 437.80 199.80 92.14 163.47 129.84 0.83 0.53 68.75 131.15 172.96 32.32 26.84 29.71 151253.99
Paste Plant 431.00 261.00 105.00 182.00 150.00 0.82 0.56 83.33 151.52 202.97 30.48 58.03 31.39 183318.96
Paste Plant 417.00 182.00 85.50 129.00 97.00 0.75 0.74 71.72 97.98 135.66 31.02 46.34 42.61 157793.26
R/R Shift elec room 421.00 153.04 70.00 110.00 78.00 0.70 0.88 68.46 78.79 108.05 31.21 44.99 50.01 150615.34
Pot line 3 421.00 61.00 23.00 42.30 35.50 0.84 0.50 17.87 35.86 49.18 6.44 11.82 28.01 39318.97
Pot line 3 431.00 68.81 23.47 33.26 23.64 0.71 0.85 20.08 23.88 31.99 9.38 36.82 48.57 44172.53
Pot line 2 421.00 58.99 29.47 45.27 34.28 0.76 0.71 24.43 34.63 47.49 10.64 11.50 41.07 53746.69
Pot line 2 431.00 86.93 49.29 63.35 39.76 0.63 1.09 43.35 40.16 53.80 23.19 33.13 59.50 95361.83
Pot line 1 420.00 52.00 21.00 37.10 30.70 0.83 0.54 16.66 31.01 42.63 6.09 9.37 30.56 36641.60
Pot line 1 431.00 87.28 46.52 62.59 41.92 0.67 0.97 40.47 42.34 56.72 20.25 30.56 54.20 89043.13
Above G shift office 421.00 426.00 220.00 311.00 242.00 0.73 0.79 192.08 244.44 335.24 66.56 90.76 45.63 422585.41
Rodding Room 424.00 175.29 100.23 120.07 65.99 0.55 1.38 90.80 66.66 90.77 53.41 84.52 69.14 199763.32
Cathode MCC 411.00 129.00 45.50 90.00 76.50 0.86 0.45 34.69 77.27 108.55 12.73 20.45 24.71 76327.62
Cathode MCC 431.00 18.00 7.50 11.10 8.10 0.75 0.74 5.99 8.18 10.96 2.92 7.04 42.61 13176.55
Paste Plant 416.00 200.00 33.70 48.00 33.00 0.72 0.82 27.10 33.33 46.26 14.67 153.74 47.11 59630.78
Paste Plant 422.00 156.89 84.91 113.02 73.69 0.66 1.00 73.38 74.43 101.84 38.59 55.05 55.56 161435.31
Paste Plant 426.00 172.28 85.83 130.86 98.89 0.76 0.71 70.48 99.89 135.38 30.97 36.90 41.07 155046.98
Paste Plant 423.00 96.73 49.18 56.36 27.70 0.49 1.64 45.33 27.98 38.19 28.38 58.54 75.50 99730.33
Paste Plant 421.00 238.68 89.20 169.38 143.62 0.85 0.48 68.54 145.07 198.95 24.31 39.73 26.28 150794.47
B/F NO 5 431.00 7.10 4.60 5.10 2.20 0.42 2.02 4.44 2.22 2.98 2.88 4.12 82.00 9768.47
Near inst office 426.00 52.60 31.90 30.50 23.00 0.43 1.96 45.01 23.23 31.49 7.27 21.11 81.13 99029.75
Near inst office 426.00 62.40 29.70 32.60 13.20 0.41 2.06 27.14 13.33 18.07 19.27 44.33 82.51 59713.33
R/R 423.00 55.00 25.30 36.10 25.80 0.71 0.84 21.70 26.06 35.57 10.04 19.43 48.13 47729.91
Near W Shop 421.00 175.75 90.60 132.42 96.34 0.73 0.79 76.47 97.31 133.46 35.11 42.29 45.63 168230.90
Near W Shop 423.00 132.46 63.99 97.03 73.72 0.75 0.74 54.51 74.46 101.64 22.57 30.82 42.61 119922.88
Near W Shop 417.00 127.58 69.00 91.70 68.00 0.34 2.62 178.40 68.69 95.10 23.01 32.48 88.21 392470.35
B/F NO 5 427.00 128.61 57.43 83.72 63.25 0.73 0.79 50.20 63.89 86.39 19.83 42.22 45.63 110448.46
B/F NO 5 423.00 220.42 106.81 168.13 129.65 0.77 0.69 88.96 130.96 178.75 37.17 41.67 39.51 195706.61
Total 3937.63 1800.77 2679.43 1994.29 1661.37 2014.43 2748.00 665.00 1189.64 3655022.43
Present Annual KvaH
Requirement = 2,34,71,806.80
After Power Factor
Improvement = 1,76,46,444.85
Total Saving in KvaH = 58,25,361.95
Annual saving Kvah Charged
@ Rs 4 Per Unit = 2,33,01,447.81 Two crore thirty three lakh only
Monthly saving = 1941787.32
Total Investment = 36,55,022.43
Payback period = 1.88( Approx two Months)

31. The End
Vidya Sagar
vidya.sagar@adityabirla.com
B.Tech Electrical (JMI Delhi)
Hindalco Industries LTD.
PH-9795456393