Research On Identification Method Of Single-phase Grounding Fault Based On Negative Sequence Characteristics

In the Power Distribution System,single-phase grounding fault is a fault with the highest probability.In this case,if the system is not timely troubleshooting,it will cause damage to the equipment and even expand the scope of the fault.At present,single-phase grounding line selection device criterion based on zero sequence voltage limit and selected faults line by zero sequence current as the characteristic quantity.However,Other asymmetric faults will cause the miscalculation in the identification of single-phase grounding fault.The zero sequence current signal is weak and easy to be disturbed.It can caused the fault line selection inaccurate.Therefore,it is of great significance to research the identification of single-phase grounding fault.Aiming at the problem of the recognition of single-phase grounding fault type,this paper detailedly analyzes the fault characteristics and sequence characteristics of the fault,including single-phase grounding fault,ferromagnetic resonance,single-phase disconnection,double-phase disconnection and double phase-grounded fault.According to the variation regulation of zero sequence voltage and negative sequence current when all kinds of faults occur in neutral grounding system.It is concluded that it is difficult to distinguish all fault types only by the criterion of zero sequence voltage but the negative sequence current changes obviously between single-phase grounding fault and other asymmetric faults.Considering the asymmetry of the system itself or the interference of the external signal,a method is proposed that the paper recognizes single-phase grounding fault and other asymmetric faults by the value of space negative sequence current that is used as the fault criterion on the basis of the limit of zero sequence voltage.This method improves the reliability of single-phase grounding fault identification.Aiming at the problem of weakly zero sequence current signal of single-phase grounding fault,this paper mainly analyzes the difference of distribution of negative sequence current and zero sequence current in distribution network The negative sequence current component is chosen as the fault feature.According to significant difference in the magnitude of the negative sequence current of the fault line and the non-fault line,a method is proposed that the paper discriminates the fault line by the value of space negative sequence current,improving the accuracy of the fault line selection.Through the simulation reliability analy sis of the criterion of single-phase grounding fault criterion by the system operation mode,the system oscillation,the grounding resistance and the position of the fault point.The result shows that the introduction method of the paper,the negative sequence current is used to identify the fault type and fault line,has good adaptability and practicability.