The Simulation Research Of UHV GIS Disconnector Switching Short Bus

With the rapid development of Chinese UHV power grid,GIS substation with its own advantages has been widely used,but GIS disconnector operation will produce very fast transient overvoltage(VFTO),which poses a serious threat to the insulation of electrical equipment.This paper comes from the project of "The key technology research of UHV GIS substation VFTO",and deeply studied the influence of the disconnector contact design on the VFTO.By solving the three-dimensional electric field of UHV GIS disconnector,calculate the distribution of contact gap electric field,using streamer breakdown criterion to obtain UHV GIS disconnector contact gap breakdown voltage curve;on the basis of theoretical analysis,construct the breakdown arc and arc quenching conditions of disconnector gap,according to the national standard "AC isolating switch and grounding switch",using the EMTP/ATP electromagnetic transient simulation software,build the electromagnetic transient simulation model of repeated breakdown while UHV GIS disconnector switching short,then simulate and analyze of the factors affecting the whole process of disconnector operation.(1)Analyse the formation mechanism of VFTO during the operation of UHV GIS disconnector,and research the influence of the arc model parameters on the VFTO.Simulation results show: if the contact gap breakdown delay increases,VFTO gradient becomes smaller;and if the steady-state arcing resistance increases,VFTO waveform attenuation is fast,and has a certain degree of inhibition of VFTO.(2)Finite element method is used to calculate the UHV GIS disconnector's three-dimensional electric field,using the streamer criteria theory to obtain the breakdown voltage value under different gap distance,the breakdown voltage increases linearly with the gap distance approximately;through the analysis of the mechanism of disconnector's repeated breakdown process,receive the gap breakdown arc and arc quenching conditions,according to the the GIS element equivalent models,establish the simulation model of repeated breakdown,simulation results show: disconnector power side voltage waveform is the superposition of high frequency oscillation pulse and sinusoidal voltage,load side voltage waveform is the step form;each breakdown,if the breakdown voltage increases,the high frequency oscillation pulse amplitude increases and the maximum oscillation pulse amplitude is about 1.2p.u,so the gap distance is larger,the VFTO amplitude is larger;the operation process produced several high frequency current VFTC,the amplitude increases gradually in the opening process,and its amplitude decreases gradually in the closing process.(3)Study of the influence factors of repetitive breakdown process.Through the analysis of influence factors of UHV GIS disconnector electric field distribution,simulate the electric field of different contact curvature radius: the larger radius of curvature,the greater the gap breakdown voltage;then bring the different breakdown voltage curves into the contact repeated breakdown simulation model,the probability statistics shows: the radius of curvature of contact is larger,high VFTO production probability is greater,breakdown times and repeat breakdown duration decreased gradually;the simulation of the closing process of different short bus residual voltage,the residual voltage amplitude is higher,the VFTO value is larger,breakdown times and repeat breakdown duration increased gradually.