Harmonics - A Major Power Quality Threat

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Harmonics Analysis 

1. Harmonics are the by-products of modern day power-electronics.
2. They are created by non-linear loads that draw current in abrupt pulses and generate bad current.
3. Non linear loads causes Harmonics, Non linear loads Inject harmonic current into AC mains .




EQUIPMENTS THAT GENERATE HARMONICS: 

1. Variable Frequency Drive (VFD) - Motors
2. Welding Machines
3. Equipment with Adjustable Speed Drives
4. Conveyor Systems
5. Equipment using SMPS
6. Battery chargers
7. UPS, Personal Computer
8. Laptops , Televisions.
9. Medical Equipments
10. Servers, storage devices
11. SMPS
12. Xerox machines, faxing machine
13. Computers , laser printers.
14. Led lighting's , CFL lamps , Electronic dimmers .
15. Motors
16. Power Transformers, Generators.
17. Arc welders , induction welders
18. Rectifiers, Inverters .
19. Induction heating .
20. Flexible AC transmission systems (FACTS) .
21. Air conditioning, HVAC systems .
22. Fluorescent lighting , Electronic ballasts .
23. All Power Electronic & Electronic devices.


Harmonic Sources




SYMPTOMS & EFFECTS OF HARMONICS

1. Overheating in Neutral conductors / Transformers.
2. Increased Rms value of supply current .
3. Increased losses, Poor Power factor .
4. Nuisance tripping of circuit breakers
5. Computer malfunctions
6. Current surges damaging capacitors and fuses
7. Frequent Motor burning
8. PLC / PCB components failure.
9. High neutral-to-ground voltage often greater than 2 volts
10. communication errors, overheating and hardware damage.
11. High voltages and circulating currents caused by harmonic resonance.
12. Generator Hunting
13. Electronic Control Clock errors
14. Quivering Monitors and CRT displays
15. Equipment malfunctions due to excessive voltage distortion
16. Nuisance tripping of circuit breakers
17. Metering errors needs true metering
18. zero-crossing noise
19. skin effect
20. Reducing system power factor, resulting in penalties on monthly utility bills overloading of Neutral.
21. Deterioration or failure of power factor correction CAPACITORS.
22. Malfunctioning of microprocessor-based equipment.
23. Resonance that produces over-current surges. In comparison, this is equivalent to continuous audio        feedback through a PA system. This results in destroyed capacitors and their fuses and damaged surge suppressors which will cause an electrical system shutdown.
24. Higher energy consumption and High Current Load.
25. Increase in Reactive power consumption.
26. Dielectric break-down, interference with communication systems, signal interference and relay and        breaker malfunctions.
27. Debating of distribution system .
28. Electric machines, noise, vibrations, overvoltages .
29. Negative-sequence currents in generators and motors, especially⁸ rotor heating.
30. Reduced life cycle of Equipment.
31. Capacitor bank failure due to Overload, Resonance , Harmonic Amplification & nuisance fuse                 operation .




DAMAGE DUE TO HARMONICS

1. Equipment / Production downtime.
2. Replacement of Motors / Drives.
3. Production scrap due to communication  errors.
4. Fire Accidents. 
5. Voltage Regulation or Voltage fluctuation .
6. Debating of cables & Feeders .
7. Reduced life of Electrical Equipment like Transformer, Power capacitor , Switchgear , Cables .
8. Harmonics can cause stress on equipment and the electrical distribution network, causing increased maintenance costs and downtime.
9. Harmonics stress may go unnoticed until there is a complete Equipment failure.








Harmonics in Ups 





















Note : As per standard CEA Regulations , 

Total voltage Harmonic Distortion  %Vthd < 5%

Total Current Harmonic Distortion % iThd < 8% .



   Harmonics Mitigation Techniques :-

          1. Active or Passive Harmonic Filter (Tuned or Detuned).         

          2. Power Factor Correcting Capacitor (APFC-  Detuned and non Detuned).

3. TVSS ( Transient voltage surge Suppressor ).

          4. Passive , Active , Hybrid Filters .

5. Inline Reactor or Chokes .

          6. K factor transformers (K = 1 to 20) based on harmonic levels.

7. Neutral blocking Filter .

          8. Static Var Generator .

9. Statcom (distribution Statcom). 

10. Pdu with Delta-Star Isolation Transformer.              

11. Using Full size or Double size for Neutral instead of 3.5 core cable .          

          12. Derating of T/F , Cables , Generator . 

          13. ULTRA ISOLATION Transformer (Delta Zigzag Connection) DZn0 .


                                                                                    

ACTIVE HARMONIC FILTER


ISOLATION TRANSFORMERS



Tools for detecting Power Quality : 

1.  Power Quality clamp meters .
2. Power Quality Analyzers .
3. Voltage event recorder systems .
4. Power Quality & Motor Analyzer.
5. True Rms Meter .























Location: India

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