Probabilistic single line-ground fault location in non-effective grounded system

When a single line-ground fault occurs in non-effective grounded system, the distribution network can still operate several hours because current circulating through the fault point is small. If the dispatchers in control center fail in locating a single line-ground fault, they will have to trip feeders sequentially to locate and isolate the fault by trial and error. The tripping sequence of feeders affects Loss of Load (LOLd), unplanned service interruption, and fault duration. Feeders fault probability and loading level interweaves to determine the loss brought by trial tripping. However, current regulation does not specify clearly how to balance between these two factors. Usually, the tripping sequence is simplified for ascending in loading to minimize the LOLd. This is not an optimal scheme since feeders fault probability is not considered. Sometimes, dispatchers form tripping scheme to reduce the loss according to their experience, but these schemes are not considered as scientific method since no theoretical analysis have been presented. In order to provide scientific base and prove validity of the schemes considering fault probability of different feeders, statistic of fault in two distribution networks with notable difference, Changsha Electric Power Corporation (CEPCO) and Wenzhou Electric Power Corporation (WEPCO), are investigated in the paper. The statistics unveiled skewed spatial probability distribution of fault in distribution systems. The performance of the schemes considering fault probability of feeders is analyzed using real system data. Numerical simulations show that an improved scheme could reduce loss notably as compared to other schemes.

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