Research On Fault Location Of Small Current Grounding Based On Transient Recording Fault Indicator System

Distribution network in China often adopt the way of neutral point of effective operation,the operation mode can obviously improve the power supply reliability of the system,but also exist in single-phase grounding is the small current grounding fault,such as weak fault current,grounding electric arc unstable faults,which is difficult to It is difficult to find out the fault location.Fault indicator can quickly lock the section of fault point after fault,and has unique advantages in distribution network location.At present,the location technology based on fault indicator has become a research hotspot in recent years,but it is still difficult to accurately judge the fault through high resistance grounding.In order to improve the accuracy of location in high resistance ground,this paper studies the method of line selection and section location for small current ground fault.Firstly,this paper summarizes the principles and shortcomings of the existing location methods,analyzes the transient and steady-state characteristics of the singlephase ground fault in the distribution network,and points out that the amplitude of the transient quantity is more obvious than that of the steady-state quantity,and the fault location using the transient component has more advantages.and the simulation model of the small current ground system is established by using the Matlab/Simulink platform to verify the transient steady-state characteristics after the fault.Secondly,a line selection algorithm based on transient zero sequence energy in special frequency band is proposed.In view of the existing methods of fault line selection using transient components,which have the problems of short fault set-up time and poor accuracy of fault line selection when the phase voltage is low,this paper starts with the phase frequency characteristics of the zero mode network,studies the distribution law of transient zero mode current in a special frequency band,and gives the range and calculation method of this frequency band.Based on the constraint relationship between the zero mode current and the zero mode voltage in the characteristic frequency band,the algorithm of line selection is developed.The simulation data of all kinds of faults are imported into Matlab for verification.The results show that the algorithm has good accuracy of line selection in different fault conditions.Finally,aiming at the problem of fault section location,this paper uses the transient recording fault indicator to distinguish the fault section according to the waveform comparison.The theoretical analysis and simulation results of the distribution characteristics of the zero mode current on the fault line show that the transient zero mode current upstream and downstream of the fault point is quite different,so a location algorithm based on the mutual distance degree is proposed.In view of the possibility of a large number of branches on the line,according to the principle of "select fault branches first,then determine fault section",a section location algorithm based on mutual distance degree is developed.By using a large number of simulation data,it is proved that the proposed method has good positioning effect in all kinds of fault situations.