The Research On Wide Area Back Up Protection Algorithm For Power Transmission Grids

Traditional backup protection is difficult to reflect the operation status of the regional power system, unable to make an optimal tripping decision for the entire system protection strategy. While wide area backup protection is an effective mean to overcome those disadvantages. This paper presents an strategy for wide-area backup protection which is based on the coordination of the centralized decision-making and hierarchical implementation. This protection strategy uses the wide area information to discriminate the fault units and makes an optimal tripping strategy, the order which determines circuit breakers to trip is delivered to the corresponding substations.This paper presents two fault identification algorithm of wide-area backup protection. One is based on genetic algorithm and information fusion. The other uses the positive sequence voltage amplitude to identify the fault area dynamically and forms the relevant fault units set based on the theory that the voltage amplitude of the bus-bar which is nearest to the fault point is the minimum, then uses the direction comparison and phase difference of positive sequence current as an secondary criteria to locate the fault. This protection is simple in principle and needs less information collected via fast communication links, can successfully identify the faulted bus and faulted line in the protected area. It has a good fault-tolerance capability. The other wide area backup protection algorithm based on genetic information technology makes use of several information including primary protection action, circuit breaker status, impedance of distance relay, fault direction. The grid fault identification mathematical model has been built by using the logic relationship between power grid information and protected devices, and been solved by globally searching the solution space via GA algorithm to identify fault devices. The simulation results on IEEE39node system show that the algorithm is capable of discriminating the fault fast and accurately, and has excellent fault-tolerance capability.