An improved algorithm for fault location in distribution network

Fault location is a difficult problem when a single-phase earth fault occurs in distribution network in China. The signal injection method is the most effective way of localizing the single-phase earth fault at present. But it can not automatically localize fault presently. An algorithm of automatically localizing the fault point based on the signal injection method is proposed. It takes the signal detectors fixed to FTU along the fault feeder as nodes. The assigned positive direction is that the injected current is from bus-bar to fault point. The network describing matrix C is formed by the assigned positive directions. The information vector S of injected signal is constructed according to the detected results from each detector of the injected signal. The zero sequence fault current information vector F is constructed according to the information of zero sequence fault current from each FTU. The fault information vector G is formed by integrating vector S with vector F. The fault judgment matrix D is formed by adding the elements of vector G to the diagonal of the describing matrix C. The failure criterion and the algorithmic process of automatically localizing the fault point are proposed according to the fault judgment matrix D. Thus the automatic fault location is implemented. The algorithm is simple. And the automatic fault location based on the signal injection method is implemented. This algorithm applies in the tree fault feeders which have branches or not. Case simulation results show that the proposed algorithm is correct, effective and precedence.