1. Effects of Harmonics on Capacitors Electrical System

2. What are Harmonics? Definition:
25. April 2018
Definition:
Harmonics are integral multiples of some fundamental
frequency that, when added together, result in a
distorted waveform.

3. What are Harmonics? f(x) = sin(x) f(x) = sin(5x)/ 5
25. April 2018
f(x) = sin(x)
f(x) = sin(5x)/ 5
The resulting wave shows a strong departure from the smooth
waves comprising it:
f(x) = sin(x) + sin(5x) / 5

4. Where do they come from?
25. April 2018
The power company typically supplies a reasonably
smooth sinusoidal waveform: Supply Frequency-50 Hzs

5. Typical Harmonics are 3rd,5th, 7th & 11th
Where do they come from?
...but nonlinear devices will draw distorted waveforms,
which are comprised of harmonics of the source:
Typical Harmonics are 3rd,5th, 7th & 11th
3rd = 150 Hzs.
5th = 250 Hzs.
7th= 350 Hzs.
11th = 550 Hzs

6. Typically from Non Linear Loads like:-
How do they Originate ?
Typically from Non Linear Loads like:-
Variable Speed drives
SCR Drives
Computers
Arc / Induction Furnaces
UPS etc.
SMPS
VOLTAGE
CURRENT
LOAD
6-Pulse Rectifier
Magnetic Core
Saturation also causes harmonics

7. Problem Caused by Harmonics
Overheating of transformers (K-Factor), and rotating equipment
Increased hysteresis losses
Neutral overloading / unacceptable neutral-to-ground voltages
Distorted voltage and current waveforms
Failed capacitor banks
Breakers and fuses tripping,Unreliable operation of electronic equipment, and generators
Erroneous register of electric meters
Wasted energy / higher electric bills - KWD & KWH
Wasted capacity - Inefficient distribution of power
Increased maintenance cost of equipment and machinery
Cogging & Crawling of Induction Motors

8. Sequences Of Harmonics
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Sequences Of Harmonics

9. 3rd Harmonic in the Neutral Conductor
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3rd Harmonic in the Neutral Conductor

10. Resonance? I  IL Ic Z U ... ... I  I  I if fr = f Xc  0 Ic  
25. April 2018 DC AC
I  Ic IL U Z
11 kV level
132 kV level
if fr = f
Xc  0
Ic  
I 
Capacitor bank
Transformer
1000 kVA, uk = 5 %
DC drive
600 kW
cos  = 0.65
...
415 V level
Transformer
630 kVA, uk = 5 %
Capacitor
bank
300 kW
cos  = 0.65
...
415 V level
3 ˜
I 
Parallel
resonance
Series
resonance I

11. Harmonic Mitigating Solutions
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Active Filters
Tuned Filters
14% Detuned Filters
7% Detuning Filters

12. De-tuned harmonic filter
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13. Customer benefits of detuned filters
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Improvement of Power Factor
Reduction of harmonics
Reduction of ohmic losses, real kW energy savings
Elimination of power utilities penalties on low power factor
Power Quality improvement
Reduction of new investment for distribution equipment (transformers, LV switchgear )
Reduction of equipment maintenance cost and down time of production equipment
Improvement of production process stability

14. Tuned harmonic filter
25. April 2018
A typical tuned filter bank at 50Hz fundamental frequency consists of :
1 filter for the 5th harmonic ( 250Hz), tuned to 245 Hz
1 filter for the 7th harmonic ( 350Hz), tuned to 345 Hz
1 filter for the 11th harmonic (550Hz), tuned to 545 Hz

15. Tuned harmonic filter Switching sequence of tuned filter: LIFO
25. April 2018
Switching sequence of tuned filter: LIFO
Switching in:
3rd
5th
7th
11th
3rd
5th
7th
11th
Switching out:

16. What is De-Tuned & Tuned ????
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Ex. 25 KVAr/ 440 Volt Capacitor Xc = (KV * KV) / MVAr
Simple Capacitor
De-Tuned
Tuned

17. Selection Of Capacitor Voltage
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Overvoltage on Capacitor Terminal because of Reactor:-
100-P
Vc = Vsyst
Where Vc = Capacitor Voltage, Vsyst = System Voltage , P= De-tuning factor ( 7% OR 5.67 % )
7% Reactor Causes Over Voltage of 7.5%
System Voltage = 440 Volt
Over Voltage because of Reactor = 33 Volt
Over Voltage because of Harmonics, Voltage Variations etc. Say 10%
Select voltage rating of Capacitors as ( )= Approx- 525 Volt
Select Suitable
Voltage
Rating

18. Active filter
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19. Harmonic Mitigating Solutions
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Active Filters
Tuned Filters
14% Detuned Filters
7% Detuning Filters
Technology
Cost

20. De-Tuned Filter is a best solution
25. April 2018
De-Tuned Filter is a best solution
Conduct Harmonic Study
&
Ask for Solution

21. System Study is Necessary
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Current THD-58.5%
Current THD-38.8%

22. CASE STUDY Rolling Mill in Durgapur PROJECT
25. April 2018
CASE STUDY
Rolling Mill in Durgapur
PROJECT
Implementation of Power Factor Correction
CHALLENGE
Power Factor Improvement in Harmonic Polluted Load
Energy Conservation
The Initiative

23. CASE STUDY Project Overview Total Connected Load: 4830 kW
25. April 2018
CASE STUDY
Project Overview
Total Connected Load: 4830 kW
Type of Compensation: Centralized
Neighboring Industries-Mostly Steel.
Capacitor Bank: 1400 KVAr ( Not in Use)
Power Factor- < 0.85
Problems Faced
Very High Currents Drawn by Capacitors
Tripping of Circuit Breaker.
Heating of Cables

24. >40% load was Non-linear
CASE STUDY
25. April 2018
MCC-3
150 KW
11000 V / 433 V
2000 KVA
% Z= 5.65%
-- 6 X 200 KW---
DC Motors
400 KVAr
TR-3
% Z= 5.60%
TR-2
600 KW
500 KVAr
MCC-2
930
475 KW
11 KV Incoming
Measuring Point-1
Measuring Point-2
Measuring Point-3
Measuring Point-4
Neighboring Unit
Single Line Diagram
Action
Study of Single Line Diagram & Details of neighboring industries
Details of Load
>40% load was Non-linear
Harmonic study of System:
Under various conditions
Without Capacitors
With Capacitors in Ckt.
All Capacitors OFF
50 KVAr ON
200 KVAr ON
Voltage THD

25. CASE STUDY Current THD Resonance frequency
25. April 2018
Current THD
Resonance frequency
By calculation also resonance frequency for
KVAr Capacitor falls between 550
& 650 Hz i.e. 11th & 13th harmonic order.

26. Result PF >0.98 Reduced Bill
CASE STUDY
25. April 2018
Conclusion
11th & 13th harmonics are pre-dominant in system.
Harmonics are getting amplified because of resonance circuit which is getting
created between capacitors and transformer.
It was also observed that most of the harmonics are Coming from main in-coming
supply from 11 KV side.( 6.6% of Voltage THD was measured)
Solution
All the capacitors were replaced with new harmonic filter and capacitors rated
for 525 V were used in this application.
Result
PF >0.98
Reduced Bill

27. 25. April 2018
Thank you