Wednesday, May 15, 2013
Effects of Harmonics
1. Over voltage and excessive currents due to series and parallel resonance some of the harmonic components in voltage and currents get amplified because of the resonance between system inductive and capacitive elements.
2. Increase in losses and consequent heating of transformers and rotating machines. Higher order harmonics will lead to increase in frequency dependent losses and losses due to skin ` effect.
Further, the negative sequence harmonic content such as 8* etc cause additional heating in rotating machines.
3. Overloading of power factor correction shunt capacitors leading to excessive leading of current to excessive fuse blowing. This is because the capacitance offers lower reactance to higher frequency harmonics (Xc is proportional to 1/10- Sometimes occurrence of series or parallel resonance at one or more of the harmonic frequencies will result in failure of shunt capacitors and other connected equipments.
4. Aging of insulation of the electrical equipments. Hence reduction in efficiency of power generation, transmission, and its utilization.
5. Increased error in energy meters. Studies have indicated that there will be a decrease in energy recorded due to the presence of harmonics.
6. Mal functioning of protective gears such as relays, circuit breakers due to changes in voltage and current caused by the harmonics.
7. Inductive interference with neighboring communication network. The harmonic existing in the power line caused interference in the adjacent communication lines thereby corrupting the messages being transmitted on the communication networks.
8. Tripping of machines at smaller loads.
9. Fire hazards.
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