Research On Diagnosis Method Of Medium Voltage Line Grounded Fault Based On Fault Indicator

As a bridge connecting the power system and the end user,the distribution network has caused frequent failures in the distribution network due to the complexity of its own structure,and most of the power outage problems of the end user are also caused by the distribution network failure.How to quickly and accurately identify the fault type of the distribution network is very important to build a strong intelligent distribution network.As a fault monitoring device widely used in medium voltage distribution networks,fault indicators have the problems of false alarms and omissions in the detection of single-phase ground faults,so it is of practical engineering significance to study how to improve the recognition rate of single-phase ground fault indicators.In this paper,the transient recording fault indicator of overhead line of distribution network is taken as the research object,and the problem of high single-phase grounding false alarm rate is improved in fault diagnosis criterion and hardware circuit design.First,the characteristics of single-phase grounding faults in the three types of grounding,neutral grounding,high-resistance grounding and arc-extinguishing coil,are analyzed.According to the nature of the grounding resistance,the single-phase grounding fault is divided into For a fixed resistance grounding and arc light grounding fault,and its fault characteristics were analyzed in detail.Secondly,the working principle of fault diagnosis of fault indicator is introduced,and in view of the shortcomings of current fault diagnosis methods,a simple and practical fault diagnosis criterion is determined.This criterion is to use the mutation of each phase current when different types of faults occur on the line.Fault diagnosis based on the difference of the quantity and electric field.Finally,build a 10kV distribution network model in Matlab simulation software,simulate to obtain line fault information,and verify the accuracy of the proposed fault criterion.The simulation and experimental results show that the accuracy of the criterion is not affected by the neutral grounding method of the distribution network,the nature and size of the grounding resistance,the initial phase angle of the fault,and the fault distanceDeveloped a prototype of a fault indicator based on a low-power microcontroller,and completed functional and performance tests.The multi-power supply scheme of the fault indicator is designed,and the electromagnetic induction self-power of the current transformer is used in conjunction with the super capacitor and battery power supply to improve the reliability of the power supply of the fault indicator under various working conditions.Combined with power grid fault simulation and fault indicator processing,the effective feasibility of the fault diagnosis method and the accuracy of the fault diagnosis criteria are verified.