EFFECT OF GENERATOR GROUNDING METHOD ON TRIPLEN HARMONICS PRODUCED BY SYNCHRONOUS GENERATOR

Salient pole synchronous generator is one of harmonic sources that cause various power system harmonic problems especially related to neutral. This paper is aim to study the characteristic of third harmonic voltage and current from generator when connected to balanced load, generator load connection with different generator neutral grounding resistor and generator load connection shunted by zig-zag transformer. Lab scale experiments have been conducted to vary all parameters related generator neutral grounding resistor and reactance earthing under various combined resistive and inductive load. The value for NER and reactance earthing is varied for each combined resistive and inductive load. Zig-zag transformer is connected to various combined resistive and inductive load. Generator neutral grounding resistor can effectively reduce the third harmonic in the phase and neutral. However care should be taken not to use very high generator neutral grounding resistor that can also restrict earth fault current that may pose problem to the sensitivity of earth fault protection system. Zig-zag transformer efficiently divert third harmonic current from generator to enter the load but high circulating third harmonic current between generator and zig-zag transformer may pose heating problem to the equipments. Reactance earthing can greatly reduce the third harmonic in the phase and neutral compared to both NER and zig-zag transformer.