Third Harmonic Current in a Generator Neutral Earthing Resistor Connected to a Large Cable Network

A large grid-connected private industrial and residential 11 kV network in northern Australia has its own 11 kV diesel generators to supply essential loads during grid supply outages. The generators each have a neutral earthing resistor (NER). When islanded from the grid, one NER provides the system reference. Significant circulating current was causing overheating of the NER. This paper describes the investigation undertaken, the options considered for rectification and the results from commissioning of the implemented solution.