The cause of false operating of the rotor ground fault protection based on the AC injection method

In this paper we tackle the issues of the protection of a synchronous generator field winding in the case of the first ground fault. We analyze the reasons of false operation of the rotor ground fault protection based on the AC injection method on the synchronous machine with a static excitation system. This paper presents the results of the measurements on a ground rotor fault protection of a synchronous generator. These measurements were aimed primarily on harmonic analysis of the field voltage and the current flow through the insulation system of the rotor and also through the rotor ground fault protection during a failure-free steady state of the generator. This submission includes also our results of computer simulations that prove the causes of incorrect operation of the rotor ground fault protection based on the AC method.