15 years of experience with 100% generator stator ground fault protection— What works, what doesn´t and why

This paper discusses the application of three different 100% stator ground fault protection schemes. Two third-harmonic methods and a low frequency-injection method are discussed. Third-harmonic schemes have been widely applied on generators within the U.S. to provide stator ground fault protection over the entire stator winding. This paper discusses situations in which third-harmonic schemes will work and outlines the limitations of such schemes. It also discusses the use of low frequency-injection schemes which are gaining acceptance in the U.S.