Analysis And Location Of Single-phase Open Fault In Ungrounded System

In distribution networks,open faults have become one of the common faults.Especially after the application of insulated conductors,the probability of open faults increases.Singlephase open faults will cause a large number of motor phases to run out of phase,heat and even burn out;if the line is sagging after the open,it is prone to serious consequences such as burnt land,forest fires,and human and animal shocks.At present,there is no effective detection method for open faults.Therefore,how to quickly and accurately segment locate open faults,take measures to eliminate faults,restore power and supply to minimize the losses caused by open faults have important practical significance to accelerates the pace of smart grid construction,improve the reliability and stability of power supply.This article takes the ungrounded system as the research object,aiming at various types of open faults that may occur,including single-phase open and ungrounded faults,single-phase open faults with power-side grounding,and single-phase open faults with load-side grounding and a model of fault is established.Line breaking location,the ratio of the fault line grounding capacitance to system grounding capacitance,load impedance magnitude and distribution factors and the size of grounding resistance factors have been taken into consideration.Changing characteristic of offset voltage at neutral point,line voltages and phase voltages between the upstream and downstream of the breaking point are analyzed.The results show that there is a significant difference between the three-phase voltages and the line voltages before and after the fracture;fault phase voltage will increase and the two sound phase voltages may be reduced under specific conditions.The variation of three phase voltages is completely different from the traditional non-solid effectively grounding faults.According to the fault characteristics,the methods to segment locate the fault zone by using the amplitude and phase of the phase voltage and the line voltage is proposed.These methods can be applied by distribution automation platform or malfunction indicator system.It can improve reliability and applicability of line break fault location.Finally,using MATLAB simulation software to set up the distribution circuit simulation model,the theoretical analysis of the fault characteristics of different open fault types including the offset voltage at neutral point,three phase voltages and the line voltages before and after the fracture were simulated and verified;and the correctness of the proposed method to segment locate the fault section using the phase and amplitude of the phase voltage and the line voltage is verified.Through the work of this paper,the deficiency of the existing single-phase open fault location method is made up,and it is of great significance to improve single-phase open fault processing technology and power supply reliability of the distribution network.