Cascading trips caused by flow transferring are the crucial reason for a lot of well-known blackouts. Aiming at the distance relay which is most applied in power grid, this paper puts forward an adaptive setting scheme to prevent cascading trips in complex power grid. In this paper, using two-port network model to fast calculating apparent impedance, and than calculating the apparent impedance change rate which is caused by flow transferring. According to the apparent impedance change rate modify the setting value which would contract the range of the impedance circle. After accomplishing the contraction, the relay action check will start. Through the process of modification and checking, the adaptive setting scheme which is not affected by the flow transferring will be formed. Taking the New England 10-unit 39-bus system which also used this method as the example, in this case, this method is confirmed by the BPA simulation.

Power flow transferring random occurred in power grid, so how to quickly identify overload line is a key problem to prevent cascading trips. This paper according to the bus self-impedance change rate rapid search the area which possible happened power flow transferring, and through the correction method for network equations checked the lines in this area whether overload or not, then selected the overload line caused by power flow transferring. Under the condition of known initial network parameters, this scheme according to the local network parameters modified to related calculation, improves the calculation speed, and has advantages for multipoint flow transferring recognition in complex power grid. Taking the New England 10-unit 39-bus system which also used this method as the example, in this case, this method is confirmed by the BPA simulation.