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The industry has recently become aware of the problem of severe generator damage due to stator ground faults. Two factors have been identified as contributors to this growing problem: 1)the high magnitude of available ground fault current in complex systems with multiple ground sources, and 2) the persistence of fault current through the faulted-generator neutral after its terminal circuit breaker opens. This white paper discusses typical grounding practices and ground fault protection methods for medium voltage generator stators, highlighting their merits and drawbacks. Particular attention is given to applications of multiple generators connected to a single bus. The white paper also provides an overview of the generator damage mechanism during stator ground faults. Problem areas associated with each type of grounding are identified and solutions are discussed.
This white paper is no longer available.