Precise Locating of Stator Winding Earth Fault in Large Synchronous Generators

Abstract

Neutral of large unit-connected generators is normally grounded through a large impedance; therefore, a small current passes from a stator phase to ground (PG) fault location. Consequently, locating the fault position cannot usually be performed based on a visual inspection. There are different methods for detecting the stator slot with a PG fault, which have practically been used for many years. These methods have some drawbacks such as further damages to the faulty generator, low accuracy, requiring expensive equipment, and taking long time for detection. This paper introduces a novel strategy for realizing a stator slot with the PG fault which can be used in large generators. This strategy can be easily implemented, and it is able to detect the fault location precisely. Based on this strategy, three different methods are proposed and their performances are investigated using a simulation based on the finite elements method. The simulation results are also verified using comprehensive experimental tests.