Research On Fault Line Selection And Position Methods For Small Current Grounding System

Small current grounding system is widely used in the distribution network with quality of power supply, it will continue running for 1-2 hours after the single-phase fault for 1-2 hours. However, if the fault can not be removed in time, not only will cause equipment damaged, can also cause serious electrical accidents, so study for line selection of the small current grounding fault is very important.There was a clear of characteristics of zero-sequence and steady-state signal when the system have system failure. Most line selection methods are selecting fault line with zero sequence feature of fault line, but the zero-sequence signal is very weak in the line, and affected easily by other signal interference, and is hard to catch. Single standard line selection method can only be applied in certain circumstances, when wiring changing or failure changing, the line selection has been set often does not apply.In order for small current line system selection and positioning, this paper was analyzing failure characteristics of small current grounding system, analyzing capacitive and inductive circuits of under different circumstances, there was similarity between zero sequence current and derivative of zero-sequence voltage with analyzing normal state of small current grounding system, in this paper, the fault line and the non-fault line are judged and selected with the similarity analysis. Zero sequence signal was interference very easily, when disturbed, the fault line can not accurately selected, in this paper, the signal was analyzed in frequency domain, selecting the appropriate frequency band in the frequency domain, selecting line with similarity comparison.After selecting fault line, get the fault localization and fault phase selection with using injecting signal. This paper studied the application of AC injection method, DC injection method and pulse injection method in the fault line, selecting the different parameters of the AC signal, a DC signal and a pulse signal, simulating and analyzing in different grounded systems with different grounding.