Research On The Demarcation Technology Of Fault Users In Distribution Network

In recent years,boundary switches have been widely applied in China.The demarcation switch is a device that integrates line segment switch with microcomputer protection measurement and control and communication.It is installed on the boundary between the power supply system and the public distribution network governed by the power supply enterprise.It can separate the fault line from the direct trip action,or cooperate with the superior circuit breaker(such as the substation circuit outlet circuit breaker).Fault in the isolation area of action trip can avoid user interruption on other lines when the line fails.And it can be used as the basis of responsibility differentiation between power supply companies and users.However,in the actual application process,the boundary switch has not found the suitable algorithm.In distribution network,neutral grounding or arc suppression coil grounding are adopted.In the neutral point through arc suppression coil grounding system,the power frequency zero sequence current is relatively small due to the influence of the compensating current of the arc suppression coil,and the method of detecting the fault by detecting the power frequency zero sequence current is easy to reject.Most of the distribution network faults are single-phase grounding faults.Therefore,the single-phase grounding fault in distribution network is the most important problem.Based on transient information,two algorithms are proposed in this paper,namely transient zero sequence current amplitude method and transient zero sequence current waveform similarity algorithm.The distribution characteristics of zero sequence current in zero sequence current network are analyzed,the SFB range is determined,sampling points are obtained and the effective values of transient zero sequence current are calculated,and then the fault is compared with the action values.Using this method to detect the fault section,the sensitivity can be significantly improved.In the algorithm based on the principle of transient zero sequence current waveform similarity,the fault waveform is recorded ahead of time,the transient fault waveform is extracted and the similarity coefficient is calculated.The calculation results are the basis for the fault location.The research is based on the existing hardware conditions,and has high practical application value.It has been modeled and simulated through ATP,and the data import MATLAB analysis verifies the feasibility and accuracy of the method.Finally,the dynamic simulation test is done through RTDS.The reliability of transient waveform method is verified by RTDS test results.In distribution network,neutral grounding orarc suppression coil grounding are generally adopted.In the neutral point through arc suppression coil grounding system,the power frequency zero sequence current is relatively small due to the influence of the compensating current of the arc suppression coil,and the method of detecting the fault by detecting the power frequency zero sequence current is easy to reject.In distribution network,most of the fault types are single-phase grounding faults.Therefore,the single-phase grounding fault in distribution network is a problem to be solved urgently.