Harmonics are sinusoidal wave forms. They have frequency in multiples of fundamental frequency. They are produced by equipment using frequency conversion technology. They are also generated due to power drawing pattern of non- linker loads.

Sources of Harmonic Filters
1) Automatic welding machines.
2) Uninterrupted power supplies.
3) Switch mode power supply.
4) Power Transformers.
5) Variable speed drives.
6) Medium frequency induction furnaces.
7) Invertors.
8) Rectifiers.
9) D.C machines.
10) ARC furnaces.

Therefore it is essential to record power parameters and conduct harmonic study in order to provide correct solution for the P.F. improvement and harmonic filtration.

Solutions : Depending on level of harmonics, possible solutions are designed.
Harmonics protection filters : They are used for improvement of power factor and part elimination of harmonics. They are nothing but a combination of reactors and capacitors, suitably detuned. They are useful when distortion is 15 to 40 %.

Advantages of Harmonic Filters :
a) Protect capacitors from Harmonic overloading.
b) Eliminate 20 to 50 % predominate Harmonics.
c) Avoid harmonic amplification in the system.
d) Improve power factor.

This system can be configured to operate in fully automatic mode.
The object is to eliminate high level of harmonic currents to acceptable level to comply with utility regulations. They provide traps for individual harmonic frequencies, and provide reactive power compensation at fundamental frequency.

Thus following are the direct benefits
1) Elimination of power factor penalty.
2) Reduction in Harmonic Distortion.
3) Reduction in line losses.
4) Improvement in voltage profile.
5) Release of Additional VA capacity in the system.
6) Improvement in overall power quality.
7) Improvement in Reduction in Energy bill.
8) Improvement in system reliability.
9) Improvement in life of Electrical Equipment.