Protection for Turn-to-Turn Internal Fault in Shunt Reactors using Time-Domain Approach

This paper presents a turn-to-turn internal fault detection technique using time-domain approach in a three-phase wye-connected shunt reactor. The proposed protection method is sensitive to a very low level turn-to-turn fault. An unbalanced component is computed using the difference of measured current and calculated balanced component of current in each phase. The balanced component is obtained by subtracting the zero sequence component from the calculated phase current in time-domain. The unbalanced current component for normal operation of shunt reactor is zero and that for internal fault case is non-zero. Since the phase current of the reactor is calculated using terminal voltage and equivalent inductance of each phase, the proposed method is compliant to change in system voltage. Various cases including turn-to-turn fault, simultaneous fault, unbalance in system voltage and switching of reactor are studied to validate the performance of the proposed time-domain protection method of reactor.