An adaptive distance backup protection setting scheme according to the power flow transfer

The removal of one of the transmission lines will cause power flow transfer. The transferred load of for the affected lines is different. According to the degree of the power flow transfer and using the flow transfer coefficient as the weight, this paper proposes an adaptive distance backup protection scheme. Based on the real-time flow distribution measured by the wide-area measurement system (WAMS), the flow transfer coefficient can be calculated. Then, using the coefficient as a weight, the degree of the setting impedance shrinkage can be adjusted. This scheme could not only prevent maloperation, but also identify the fault and it has the ability of enduring transition resistance. The simulation results on an IEEE 39-bus testing system illustrate the validity of the scheme.