A fault component comprehensive impedance based transformer protection principle

A novel fault component comprehensive impedance based transformer protection principle is proposed in this paper. The fault component comprehensive impedance is excitation impedance when external fault occurs, which magnitude is large and which sign is positive. In situation of internal fault, the fault comprehensive component impedance is the impedances of the transmission lines and equivalent sources of system. Which magnitude is smaller and which sign is negative. In situation of inrush current, the sign of fault component comprehensive impedance is positive and the magnitude is larger than that in internal fault situation. The proposed principle based on fault component comprehensive impedance can detect the internal fault from external fault and inrush current quickly. Simulation results show that it can immunize the maloperation when transformer is energized, and has high sensitivity and reliability.