In: Electrical Engineering
Integer multiples of fundamental frequency of lower amplitude signals impressed on the power frequency signals are called harmonics.
sources producing harmonics on power distribution side are
Non-linear loads (TV, Printers, PC, mobile, laptop,
microwave),
Switched mode power supplies, Adjustable Speed Drives, Fluorescent
lamp,Transformers, Energy saving lamps, Welding equipment,
thyristor controlled heaters and ovens.
in Radial distribution system,The harmonic currents flow from loads to power system source and PF capacitors affect the flow for atleast one harmonic, Harmonic currents due to resonance is rich in a monotonic harmonic.
the following are the effects of harmonics on different equipment present in power distribution system
Capacitors
1. In resonance, the Irms > Irated
2.180 % of rated Irms, 110 % of rated Vrms, 135% of rated kvar
(IEEE 18 – 1992)
Transformers harmonics cause Over heating of the winding increasing
conduction losses ,Eddy current loss increases considerably
in Motors, Distorted Harmonic Voltage results in additional fluxes (Vthd > 5%, IEEE 519) results in additional losses, overheating, decreased efficiency ,Vibration and high-pitched noise
Communication interference caused by Inductive coupling of neutral line with open wire telephone circuit.
on a whole harmonics tend to reduce the efficiency of the system by increasing the losses and tend to inject noise into the system.