Study On Fault Location Method For Single-Phase-To-Ground Fault Of Small Current Grounding System

The small current grounding system is widely used in middle/low voltage distribution network in China, but due to the complexity of power distribution network structure, and the special operation mode of single-phase grounding fault, the locating of feeder fault point has always been the difficulty in the study of fault location. In practice, there is almost no feeder in distribution network fault location device, and piecewise searching is still widely used to determine the fault point. However, with the improvement of distribution automation degree and the increase of power supply reliability requirement for users, especially the requirements of communication systems for power supply quality is even higher, the realization of fast and precise ranging of single-phase ground fault in small current grounding system is very necessary. It has important effect on improvement of power supply reliability.This paper first analyzes current situation of domestic and foreign fault ranging in various method, and investigates three kinds of commonly used ranging methods,meanwhile makes the comparison of the three methods of distance measurement. In the cases of neutral point non-grounding system, neutral point via arc suppression coil grounding system, and neutral point via arc suppression coil parallel connection with resistance grounding system, when single-phase ground fault occurs, the corresponding fault characteristics are analyzed, and algorithm method of neutral point via arc suppression coil parallel connection with resistance is proposed.In the arc suppression coil parallel connects with a resistance, through theoretical analysis and formula derivation, the key problems for ranging which through the arc suppression coil parallel connects with resistance grounding is solved. The matrix iteration method of node impedance which suitable for neutral directly grounded system is improved. When single-phase grounding fault occurs, a resistance is placed in neutral point,while modify the node admittance matrix at the same time, the binary iterative approximation algorithm which suitable for neutral through the arc suppression coil system is proposed.Using ATP simulation model to form neutral point via arc suppression coil parallel connection with resistance grounding system, under different transition resistance condition, the fault line/non-fault line zero order current and zero order current active power increment, zero order voltage before/after parallel resistance connection aresimulated. Combining MATLAB simulation model, the fault distance 1s simulated to verify method in this paper. The verified results indicates that this method is not affected by transition resistance, when the faults occur in different locations, this method is able to do accurate ranging measurement with high reliability.