Simulation Study Of VFTO Based On EMTP

In ultrahigh voltage and extra-high voltagesystem,The isolation switches in gas insulated substations(GIS)may produce very fast transient phenomena(Very Fast Transient,VFT)when the operation time is very high,the rise time is very short,and the frequency range is between 100kHz?80MHz.The precise modeling of GIS is the key to decide whether the fast transient phenomenon is consistent with the real principle,and the most difficult and critical part is the single arc model and the reconstruction of the reburning arcs.Considering the causes,combustion,quenching and reburning mechanism and influencing factors of GIS isolator arc,researchers at home and abroad have carried out a lot of related researches through simulation tests and simulation modeling.Based on that,a more accurate isolating switching arc model is the common goal of all researchers by reasonable numerical fitting through different methods.In this paper,we use ATP-EMTP and MATLAB simulation software to build a circuit simulation model based on a 1000 kV GIS substation,and compare some typical arc models.Based on exponential arc model,hyperbolic arc model and dynamic segmented arc model,a hybrid dynamic arc model is proposed.Based on exponential arc model,hyperbolic arc model and dynamic segmented arc model,a hybrid dynamic arc model is proposed.The hybrid dynamic arc model takes into account a series of factors such as isolation gap gap distance,peak current peak size,gas medium pressure,reignition arc and arc extinguishing criterion,etc.A comprehensive consideration of various factors that influence the generation of an arc is made.The accurate arc model can lay a good foundation for the next study of the influencing factors and suppression measures of VFTO.Based on these single arc models,the reburning arcs are simulated and studied.Based on the improved dynamic segmented dynamic arc model,a dynamic arc model based on Bergeron equivalent circuit and trapezoidal integral method is proposed.This model takes the time variant arc resistance,the time-varying arc inductance,the arc stray capacitance and the time variation of the isolation switch to take into account the arc simulation.This method is also applied to the dynamic hybrid reburning arc model.The results show that the trapezoid dynamic arc model is suitable for the computation and analysis of VFTO,which has a certain reference value for the further accurate simulation of arcing.Unlike many current arc simulation,all the single arc models proposed in this paper and the time-varying resistance of reburning arc models take into account many factors that influence the VFTO when the contacts move.Therefore,the arc extinguishing resistance of the reburning arc simulation model increases step by step with time,which is consistent with the real arcing condition,and has a certain reference value for the research of the accurate arc resistance.