Improved fuzzy logics based differential protection scheme

In this research work, fuzzy logics based differential protection scheme is proposed for power transformer. Membership functions are developed from voltage, frequency and currents at primary side and secondary side of the power transformer. The proposed protection scheme senses the operating conditions and gives trip or no trip signal to the circuit breaker from the fuzzy inference of the small, medium and high values of the membership functions. Simulation results of various operating conditions, shows that the proposed differential relay is reliable, fast and is able to discriminate between internal faults, external faults and magnetizing inrush current. Results also demonstrate selective phase switching and auto-reclosing function of the protection scheme. Fuzzy logics based protection scheme is modeled in MATLAB-SIMULINK environment.