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Harmonic Mitigation

Harmonic Mitigation
Updated: | 6 min read

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Harmonics is defined as a component of periodic wave (or a signal) whose frequency is integral multiple of the fundamental frequency. Non linear loads such as rectifiers, inverters, variable speed drives, furnaces, etc. create harmonics. 


These currents consist of a fundamental frequency component rated at 50 Hz, plus a series of overlapping currents, with frequencies that are multiples of the fundamental frequency. The result is deformation of the current (and, as a consequence, voltage) that has a series of associated secondary effects.

Fundamental Wave

The importance given to harmonics analysis in installtion design is increasing these days. If any problem occurs due to harmonics, it results in major loss of material and money. International standardisation has been tackling these phenomena for many years, although the standards and recommendations in force are yet to produce significant results in India.


There are certain cases of malfunctions linked essentially to the above phenomena; some of these are illustrated below:

Type of EquipmentEffect of Harmonics
Rotating Machines Increased power losses, over heating due to skin effect as higher frequency current flows on cable periphery increasing cable resistance, pulsating torque due to negative phase sequence harmonics
Transformer, Switchgear, Power Cables Over-heating, increased power consumption
Protective Relays Mal-operation, nuisance tripping
Power Electronics Mal-operation, failure
Power Capacitors High currents & failure due to overload
International standardisation

In harmonic rich environments, some of the following design considerations need to be incorporated in Automatic power factor correction system design:

  1. Heavy duty capacitors (Capacitors having a higher overload and peak inrush current withstand) need to be used.
  2. Depending on the nature of the non linear load, a suitable de-tuned reactor ( 7%, 14%) might have to be used.
  3. When capacitors are used along with the de-tuned reactors, the voltage that appears across the capacitor increases (as it is the vector sum of the system voltage and the voltage across the reactor). Moreover to achieve a net output of the reactor capacitor combination, a higher kVAR capacitor needs to be used that will compensate for the reactive power used up by the de-tuned reactor
  4. To achieve the desired tuning frequency 1 / (2Ï€C(LC)) of the capacitor-reactor combination (In case of a de-tuned reactor, this frequency is well below the resonant frequency of the system), the inductance-capacitance combination is of crucial importance. If a lower value capacitor is used, the tuning frequency of the combination will increase and might even coincide with the resonant frequency of the system. This can be a very dangerous condition.


Thus the capacitor reactor combination has to be selected properly for successful harmonic mitigation.


It is difficult to solve harmonics related problems, once the power factor correcting system is installed. It is important to incorporate Harmonic Mitigation techniques while the system is being designed.

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About the Author

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Sourav Dasmodak,

Product Management & Marketing (Powergear - ACB)

Product Owner of Air Circuit Breaker (ACB) of Lauritz Knudsen for Domestic & International Market. I can talk to you about Electrical Products' Sales, Business Development, Market Expansion, Cracking Critical Strategic Account, handling Key Account & of course how to develop & motivate Channels along with the organizational growth. Having near about one and a half decade of experience across the country with major electrical manufacturers (Top 4).