Direct Current System And Remote Backup Protection For Phase-to-phase Faults At The Angle-connected Side Of Transformers

Direct current system and the transformer remote backup during its designing and operating, is of the utmost importance for guaranteeing the safety of the transformer. This paper mainly discusses direct current system and the transformer remote backup protection problem, especially the problem when a fault occurs at the angle-connection side (non-battery side) of transformer, and furthermore the transformer's protection loses its DC battery. Through the vector diagram analysis of the characteristics of fault currents through both of transformer's high side and low side at the moment when two phase fault happens at the angle-connection side, a new remote backup protection scheme is proposed in this paper. The scheme completely solves the problem that the remote backup protection is not sensitive enough when the occurring of two-phase fault at the transformer angle-connection side.