Character Calculation And Fault Reason Analysis Of Transmission Line Transition Resistance Variation

With the development of economy and the improvement of industrial production efficiency in China,the requirements for safe and reliable power supply of power grid operation are higher and higher.Preventing the occurrence of significant or giant power grid safety accidents has always been an important responsibility of the power grid operation management department.Therefore,the analysis results of the causes of power grid faults are the main basis for restoring power supply and accident handling.There are many reasons for transmission line faults,among which lightning strike and pollution flashover account for the largest proportion of faults.The arc trace is often not obvious,and the cause of the fault cannot be found through on-site line inspection.If the hidden trouble is unknown and the power is transmitted blindly,the risk of accident expansion will also be caused.In order to accurately distinguish the faults caused by various reasons such as lightning strike or pollution flashover,based on the analysis of the current research status,development trend and problems of the causes of transmission line faults,the research on judging the causes of the above faults is carried out through the quantitative calculation of the transition resistance changing with time,its changing characteristic parameters and the similarity analysis of volt ampere characteristics.The main research contents are as follows:(1)A time-varying transition resistance calculation method based on transient fault recording data is proposed.The adaptive filter is used to process the recorded data,which realizes the synchronization of data and the determination of fault time.Based on the distributed parameter circuit model of the transmission line,the recursive calculation of the resistance and inductance parameters at the fault point is carried out from both sides of the transmission line to the fault direction by using the bilateral fault recording data.The fault point is determined based on the same instantaneous phase of the voltage calculated on both sides of the transmission line.The calculation of transition resistance and inductance parameters of each phase of different fault types is realized via the calculated current and voltage data at the fault point and the principle of instantaneous phase consistency of current and voltage on the transition resistance,The transition resistance calculated at different time points can characterize its variation characteristics with time.(2)The improvement of sine function fitting method based on Hilbert transform is carried out.This thesis adopts an algorithm based on sine fitting of Hilbert transform to convert discrete current and voltage signals from fault recorder into continuous signals,to meet the requirements of inputting higher-order derivatives of current and voltage in the calculation process of using distributed parameter circuit model of transmission line,as well as to obtain their multi-order derivatives,and optimizes and improves the calculation process of this algorithm.By changing the call mode of Hilbert transform,the calculation load of sine function fitting of Hilbert transform is reduced,and the order of sine function fitting is improved,simulation results show that the fitting accuracy of recorded transient data is significantly improved,which can fully meet the accuracy requirements of transition resistance changing with time and changing characteristic parameters.(3)The analysis method of lightning stroke and pollution flashover fault based on the change characteristics of transition resistance is proposed.Through the analysis of lightning stroke and pollution flashover fault mechanism,transition resistance model and related fault cases,the characteristics of the arc resistance during lightning stroke and the residual pollution layer resistance of pollution flashover fault changing with time are extracted,and the characteristic parameters of variation characteristics and calculation methods of lightning stroke and pollution flashover fault transition resistance are obtained.Based on the recording data of actual fault cases caused by multiple groups of different fault causes,the characteristic parameters of the transition resistance of each fault case changing with time are calculated.By analyzing and summarizing the calculation results,the classification criteria of lightning stroke and pollution flashover fault causes based on the variation characteristics of the transition resistance is formed,the characteristic parameter criterion index and volt ampere characteristic correlation index of these two types of fault transition resistance is obtained,and a complete transmission line fault cause judgment process is constructed.