Study Of Adaptive Ground Distance Relay

Earth fault of single-phase is the most familiar fault in transmission line of highvoltage,and the fault resistance may cause the overreach or underreach of thetraditional ground distance relay at the ground fault conditions.So how to improve thecapacity of the earth-fault resistance endurance of a ground distance relay and avoidit's overreach effectively is a pop problem in the ground distance relay research.In this paper, a adaptive operating characteristic ground distance relay isproposed.The relay takes U|·_1φ -U|·_φ as it's polarization voltage(U|·_1φ is the positivevoltage in earth fault phase, U|·_φ is the voltage in earth fault phase),and it can adjustit's operating border automatically according to the different fault resistance,so thenew relay can adapt to different earth resistance and can reflect the earth-fault up to asuper high resistance.In addition,a modification of adaptive operating characteristic isalso proposed to avoid overreach in this paper.The modified adaptive ground distancerelay can effectively avoid transient-state overreach, as well as reflect the earth-faultup to a high resistance.Many simulations and investigations about the adaptive ground distance relay arerun in 110kV and 500kV system,and the simulations show that the adaptive grounddistance relay has excellent adaptability and selectivity not only in 110kV system butalso in 500kV system,and the effect turns up trumps.