A novel protection principle for turn to turn fault of valve side winding of series transformer of UPFC project

This paper presents a novel protection principle for turn to turn fault of valve side winding of UPFC series transformer. First, with a domestic 500 kV UPFC project as the basis, the difference of connection mode of line side winding of series transformer is presented. Next, problems of traditional current differential protection are analyzed. Traditional current differential protection may have less sensitivity or even refuse to operate in certain fault cases. Then, double K zero-sequence current differential protection is proposed to overcome the problem in traditional protection scheme. Finally, RTDS Simulation tests verify the problems of traditional protection and the validity and superiority of double K zero-sequence current differential protection. The proposed protection principle has higher reliability and sensitivity and has a good applicability in practical engineering project.