Research On The Influence Of Circuit Breaker Operation On The Misoperation Of Relay Protection Device

With the increasing scale of power grid,the probability of power grid failure is increasing,and the relay protection devices occasionally act incorrectly.However,customers need a more reliable power grid,so the power supply enterprises must strictly control the power distribute network,eliminate potential equipment hazards as far as possible,reduce the rate of protection misoperation,and provide reliable power for customs.In this thesis,the overvoltage mechanism of busbar and transformer ungrounded neutral point caused by arc extinguishing during operation of circuit breaker is analyzed in depth.On this basis,the misoperation of zero sequence protection for a 110 kV transmission line is studied.Firstly,this thesis analyses the possibility of multiple arc extinguishing when circuit breaker disconnects short circuit current.Secondly,based on the structure of a 110 kV distribution network,according to the characteristics of electrical parameters and load current when short circuit occurs,the arc model is established.By analyzing the characteristics of overvoltage produced by circuit breakers operating at different speeds,the causes of misoperation of relay protection are obtained.Finally,a rectification scheme using directional distance protection as starting unit is proposed.With the addition of startup elements,the relaying will not misoperation for transformer neutral zero-sequence current path caused by circuit breaker operation,and zero-sequence current protection can operate reliably when grounding fault occurs on the protected line.The simulation results show that the zero sequence current protection with start-up elements can operate correctly when the breaker is reclosed to permanent fault which causes the neutral protection gap of transformer is broken down.While the relay protection can operate reliably when the grounding short-circuit fault occurs at the end of the line.The proposed method can improve the reliability of 110 kV transmission line at the end of distribution network.