The study of triplen harmonics currents produced by salient pole synchronous generator

Abstract

Triplen harmonics study for harmonics produced by salient pole synchronous generator is very important because their presence have caused communication line interference, damage to neutral earthing resistor etc. The purpose of this paper is to study the characteristics of triplen harmonics under balanced/unbalanced resistive/inductive loads, different generator neutral earthing resistor values and various transformer winding configurations. Lab scale salient pole synchronous generator is used for the experiment and third harmonic currents are recorded for analysis to represent triplen harmonics currents characteristics. Under balanced load, third harmonic current is inversely proportional to load impedance and neutral current is three times the phase current. During unbalanced load condition, the neutral current is lower than arithmetic sum of phase current due to different phase current magnitude and angle. The phase and neutral third harmonic currents magnitude is inversely proportional to generator NER resistance under balanced load. Transformer winding configurations under balanced load permit third harmonic current flowing through them in accordance to zero sequence network for the transformer apart from higher transformer reactive impedance at third harmonic. This study provides a very important input to mitigation method in reducing triplen harmonics currents propagation in the network.