Research and Application of Selective Stator Ground Fault Protection Based on Fibre Optical CT

According to the problems of electromagnetic current transformer used for selective stator ground fault protection, a novel scheme of selective stator-ground fault protection based on fibre optical current transformer is proposed in the paper, the electrical characteristics of internal and external stator ground fault are analyzed, the zero-sequence directional criterion of stator ground fault protection is proposed, and the key technical points are summarized. The results of static and field simulated ground fault experiments show that the scheme can accurately measure zero-sequence small current signal, it is not affected by the irregular arrangement of generator terminal three-phase conductor, and it is convenient for installation. The principle has been used on four 165MW hydropower station units of Sichuan, China, and the operation is good.