Experience of the New England System with Generator Protection by Resonant Neutral Grounding

Highly sensitive ground fault relaying for generators in unit connection results from resonant neutral grounding. This scheme has the purpose to detect ground faults in their incipient stages anywhere on the low voltage side of the generator, that is, in the generator winding, the connections from the generator to the transformer and the transformer low voltage winding. The inherent advantages of resonant neutral grounding, when applied to unit connected generators, have been over-looked in this country - at present, this method is used only for the generators of one utility system. It, is shown how resonant neutral grounding provides greater sensitivity for detecting high resistance faults than other commonly used protective schemes, and how the current at the fault is reduced to such low value that the effects of iron burning of the stator can be made harmless. Experience with this protective scheme on the New England Electric System during a 20-year period is reported.