Experiment research on differential protection for UHV transformer in China

Ultra-high voltage (UHV) transmission possesses enormous economic benefits and technical superiorities, which is a new subject for China and must be studied emphatically. This paper introduces the actual configuration and parameter of UHV transmission under construction in China and its physical dynamic simulation (PDS) experiment model. According to the structure and operation characteristics of 1000 kV UHV transformer, the paper studies and proposes the differential protection scheme of UHV transformer through analyzing a great deal of PDS experiment results. The research shows that the complete differential protection of main transformer canpsilat operate sensibly and the differential protection of the voltage regulating winding and the voltage compensating winding are needed respectively, when the voltage regulating winding and the voltage compensating winding inter-turn faults happen. These differential protectionspsila operating performance of the second harmonic restraint when switching on an unloaded transformer is analyzed.