Radial Distribution Network Earth Fault Diagnosis Method

Quick and accurate fault location is the premise to rapidly isolate the fault and redelivery power supply, and it is important to the normal working of power networks. Line-to-ground fault location maintains unresolved to power distribution networks for a long time. After a comprehensive analysis of existing methods, the author made a thorough study with the on-line monitoring method and a fault location algorithm.Based on the main fault-character analysis of single line-to-ground fault in non-grounded distribution networks, the location algorithms by injecting current are proposed for diagnosing and locating faults. Firstly, a relevant algorithm is presented for locating single-line-to-ground(SLG) fault in distribution networks, fault functions are reasoned out and analyzed for single-phase and three-phase distribution lines, and criterion measure, which are based on the frequency, phase and shape characteristics of the fault function spectrums , are also presented for locating SLG faults. Computer simulation shows that the criterion measure effectively locates faults in direct distribution line, and it is also feasible to tree-type distribution system in theory but there are still some problems in practice. In the next place, an improved algorithm of grounding fault location for tree-type distribution system which is based on new fault function and criterion measure, is proposed in order to complete fault branch identification, fault location and fault value. A lot of the simulation of fault diagnosis and location by computer demonstrate that the algorithm is effective. Universal computer program of locating SLG faults in distribution networks is worked but based on the algorithm. Since it is immune to load change, immune to the value of grounded resistance change and its parameters can be easily measured, the fault location algorithm can be widely applied to the power distribution networks.Feeder automation, which can automatically detect and isolate the ground-faulty section, is the direction distribution automation made progress to. An automatic fault location method is proposed based on FTU after the circuit analysis of single line-to-ground fault in distribution networks. In the method zero sequence voltage is discussed and new principle for automatic fault location and isolation based on the zero sequence voltage is presented in this paper. Compare to the traditional current methods, this method is not only immune from neutral grounding modes, but also more bearable to interference.