Research On Monitoring Technology Of Distribution Line Capacitor Switching State

With the rapid development of distribution network,the number of loads is increasing,which leads to the increasing loss of distribution lines.The most simple and economical reactive power compensation method is to install parallel compensation capacitors at the appropriate position of the line.However,due to the principle of on-site compensation,line capacitors have the characteristics of scattered distribution,large number,frequent switching and difficult monitoring of switching status,which makes it difficult to plan and optimize the distribution network,as well as capacitor maintenance.Therefore,real-time monitoring of the switching state of line capacitors is not only conducive to the planning and optimization of distribution network,but also of great significance to the maintenance of capacitors.In order to monitor the switching state of line capacitors,this paper analyzes and studies the identification,orientation and master station positioning of capacitor switching operations.Aiming at the problem that voltage and current transient cannot be used to identify capacitor switching operation,a capacitor switching operation identification method based on reactive power variation is proposed.Based on the equivalent circuit,the reactive power variation law at the upstream Power Quality Monitor(PQM)during capacitor switching is analyzed.The reactive power variation is calculated and the threshold is set.Combined with the detection of high frequency or DC transient current,the identification of capacitor switching is realized.The simulation model is built by Simulink,and the inductive load switching,cable switching and reactor switching that may also cause reactive power change are identified.The accuracy and feasibility of the proposed identification method are verified.Aiming at the problem that the transient characteristics have poor anti-interference ability and cannot be applied to the capacitor removal orientation,this paper proposes a capacitor orientation technology based on reactive power change.The characteristics of active and reactive power changes at upstream and downstream monitoring points during capacitor switching are derived.The relative position of the capacitor is determined by the difference in the ratio of active power change to reactive power change at the monitoring point,and the orientation of the capacitor is realized.The feasibility and anti-interference ability of the method are verified by simulation.Aiming at the problem of poor fault tolerance of the master station matrix positioning algorithm and the lack of a unified accuracy evaluation system,this paper proposes a master station positioning algorithm based on reliability.Based on the correct probability of terminal uploading information,the reliability matrix is constructed,and the secondary positioning method is proposed to improve the fault tolerance.Based on the principle of mathematical statistics,a positioning accuracy evaluation system is proposed to make up for the lack of accuracy evaluation of the current master station positioning algorithm.The fault-tolerant ability of the master station positioning algorithm and the effectiveness of the evaluation system are verified by examples and simulations.Compared with the typical matrix positioning method,the advantages of the fault-tolerant ability of the algorithm are verified.Finally,in order to verify the effect of the proposed identification and positioning method in the actual environment,a timing switching device is made based on the conditions of the laboratory,and a simulation experiment platform that can realize the timing switching of capacitors is built.Through the data obtained by Labview software and NI data acquisition board,the identification and orientation of capacitor switching operation are simulated respectively,which further verifies the feasibility and effectiveness of the identification and positioning method proposed in this paper in the actual environment.