The Research Of Comprehensive Fault Line Selection For Single Phase Grounding In Small Current Grounding Sustem Based On Cross-correlation Algorithm

With the rapid development of social economy, the power users require an increasing demand of power supply reliability, which bring new and higher requirements for the safety and the reliability of a power system. At present, most of 6kⅤ～35kⅤ distribution networks in China adopt a small current grounding system, including ungrounded systems and neutral point arc suppression coil grounding system. In particular, more than 80% single-phase ground faults occurred in the distribution network. When single-phase ground fault occurs in a small current grounding system, the current value is generally small due to a short circuit. Since the three-phase single-phase ground when the system remains symmetrical, the system is allowed to run for 1～2 hours with fault. However, if this situation continues for a long time, it will bring great negative impact on the distribution network and the equipment. This requires us to accurately determine the fault line and isolation, and to deal with the single-phase ground faults as soon as possible, which also contributes to the further development of line selection technology of the single phase to ground fault.This topic researches the advantages and disadvantages of various line selection principles based on transient, steady-state, high-frequency and "S injection", and researches adaptive dynamic contribution rate algorithm. According to the feature quantity analysis of algorithm applicable domain to solve dynamic distribution of weights in algorithms, to make algorithms can dynamically adaptive different operation modes and grounding, to achieve the dynamic contribution rate of various algorithms, and to get the accurate fault line finally.Through the cross-correlation analysis to fault components of steady-state, transient, high-frequency characteristics and injection to get the relationship between the fault line and non-fault line, to get rid of the dependence on the fault current threshold, to solve the problems of zero-sequence current threshold settings. It reduces the accuracy requirements for the zero-sequence current transformer, meet the the actual situation of substation at the same time.Current system uses a small amount of transient when the single-phase ground fault occurs, and then provides an overall design solution for the small current grounding line selection design. Meanwhile, it develops a small current grounding line hardware systems and software solution design, and then build a small current grounding system of single phase earth fault line system. Finally, we evaluate the efficacy of the proposed system.