Study on the current differential protection of transformer based on the time difference method

This paper presents a new technique for transformer current differential protection based on the time difference method. Through comparison to the traditional principles of harmonic restraint differential protection using EMTP simulation, the simulation results show that during the inrush and over-excitation conditions, the new protection technique can guarantee no malfunction; for internal fault condition, the protection can ensure fast response. The technique was implemented into a hardware platform based on a digital signal processor, the feasibility of the protection and superiority is further validated using the platform.