Research on a Distance Relay-Based Wide-Area Backup Protection Algorithm for Transmission Lines

In this paper, a distance relay-based wide-area backup protection (WABP) algorithm for transmission lines is presented. The proposed WABP collects the statuses of zone 2 and zone 3 distance relays in local substation and immediate neighboring substations. When a fault has occurred, the WABP decides whether the fault is on the protected transmission line or somewhere else. Then, it determines the appropriate time delay of tripping and acts in coordination with conventional distance relays. With the proposed WABP equipped, the setting of conventional distance relays can be simplified. The requirement of coordination between the conventional relays can be loosened and the difficulty of setting calculation can be reduced. Simulation results show that the proposed WABP can coordinate with conventional distance relays set by different methods, and it can correctly detect faults and help to reduce blackout area with fault tolerance.