Study on zero-sequence current distribution characteristics in Low Resistance Grounding mode

Low Resistance Grounding mode has been adopted in more and more megacities in China. The distribution characteristics of zero-sequence current in various cases of fault are fundamental for the proper operation of the zero-sequence current protection. Therefore, the distribution characteristics of zero-sequence current in the low resistance grounding mode are emphases of this paper. Based on Symmetrical Component Method, mathematical models and theory analysis were carried out for two-line single phase grounding fault of the same phase and of different phases. Thus, the mathematical expressions of zero-sequence current were derived. On this basis, quantitative analysis and comparison to the distribution characteristics of zero-sequence current in different cases were made, summarizing the differences between single-line and multi-line where ground faults take place. Finally, based on PSCAD/EMTDC, a great deal of simulating calculation for different cases of fault was done in order to verify the correctness of our theoretical analysis.