Analysis and improvement on stator earth-fault protection by injecting 20 Hz signal

Abstract

By analyzing the sensitivity and its influencing factors of stator earth-fault protection by injecting a 20 Hz signal, this paper puts forward an improved generator protection scheme based on the impedance angle and its mutation component. The simulation results verify this kind of protection scheme has higher reliability and sensitivity under generator neutral grounding through a distribution transformer with a secondary resistor and arc-extinguishing coil compared with the conventional criterion. Against different grounding modes, the sensitivity of the protection scheme is further improved by correspondingly adjusting the frequency of the injected signal.