In view of the influence of the transition resistance on distance protection

a new adaptive distance protection is proposed. First

according to the fault voltage and current vector distribution in the single-supply and double-supply systems

the voltage drop equation between the fault point and the relay installed location is developed and the adaptive setting coefficient is calculated. On this basis

the fault location is determined by the phase relationship between the fault current and the measured current at the relay. Finally

an adaptive distance protection criterion is developed. Simulation results based on the real time digital simulator (RTDS) show that the method proposed is able to modify the protection setting value adaptively on line

and is immune to transition resistance. Besides

it is simple in formation and easy to implement. This work is supported by National Natural Science Foundation of China (No. 51277193) and State Grid Corporation of China (No. PD71-13-031).