Research On Ground Fault Arc Of UHV Transmission Line Based On EMTP

In UHV transmission systems,grounding faults often occur on transmission lines,and 90% belong to single-phase grounding fault.Whether the secondary arc extinguishing time can be captured accurately is the key factor affecting the success rate of automatic reclosing.Therefore,this paper takes the single-phase grounding fault arc of UHV transmission system as the research object,and studies the modeling of the grounding fault arc,the judgement of the secondary arc extinguishing time of grounding and the application of the single-phase automatic reclosing.Improve the success rate of automatic reclosing of UHV transmission lines and ensure the safe and stable operation of transmission lines.The research contents and achievements of this paper are as follows:(1)The generation mechanism of single-phase grounding arc in UHV transmission line is briefly described.The traditional model of Cassie and Mayr,Schwarz and control theory model in the traditional arc model and their respective advantages and disadvantages are analyzed,and the overhead line model of transient modeling is selected.(2)For the single-phase-to-ground fault arc of UHV transmission lines with shunt reactors,the primary arc and secondary arc are combined based on the transfer function and integral module of TACS module in EMTP according to the arc conductivity differential equation and arc column energy balance theory.The dynamic characteristics of arc current,recovery voltage and arc conductance in arc dynamic parameters are simulated and analyzed.The fault dynamic arc model is applied to the single-phase-to-ground fault system of 1000 kV EHV transmission line from southeastern Shanxi to Nanyang to Jingmen in China.The validity and feasibility of the fault dynamic arc model are verified by simulation analysis and comparison.(3)In view of the accurate judgement of the secondary arc extinction time,the automatic reclosing rate is raised.A method of fault secondary arc extinguishing detection based on wavelet time-frequency entropy algorithm and all-phase Fourier transform algorithm(apFFT)is proposed.The timefrequency entropy of reconstructed voltage signal before and after fault secondary arc extinguishing is analyzed by wavelet packet time-frequency entropy technique,and the characteristic frequency band of fault secondary arc voltage is obtained.Then all phase FFT algorithm is used to analyze and calculate the characteristic frequency band,and the spectrum characteristic curve of the fault arc voltage signal before and after the secondary arc extinguishing is obtained.According to the arc simulation model established in ATPDraw and based on ATP/EMTP and MATLAB platform,the arc voltage under different closing phase angle,grounding resistance,fault location and compensation conditions is simulated and analyzed.The simulation results show that the arc extinguishing detection method proposed in this paper can accurately judge the arc extinguishing time,and is less affected by the factors such as power phase difference,transition resistance,shunt reactor compensation degree and fault location.