Research On Overvoltage And Insulation Coordination Of The AC Filter In ±800kV Converter Station

AC Filter is an essential part of HVDC transmission project.There are phenomena that AC filter arrester acts abnormally frequently and circuit breaker breaks down or crack in±800kV ultra high voltage converter staion.It reduces the operation reliability of system and adds up the cost of system maintenance,further more seriously threatens the safe and stable operation of the power system.Therefore,this paper carries out theory analysis,simulation and experimental verification on the issues of abnormal action of AC filter arrester and circuit breaker insulation level.First,based on one realistic±800kV UHVDC topology and parameters,spurious parameters of inverter station main wiring and AC filter field,high frequency voltage modeling method of AC filter is analyzed.An overvoltage simulation model of AC filter is established in PSCAD/EMTDC,and the research on the steady-state operation characteristics of the system is carried out.Then,according to the outer insulation distribution of operating AC filter circuit breaker,an equivalent model of double fracture circuit breaker with insulating pillar is built up in PSCAD.According to the inner structure and parameters of AC filter circuit breaker,a 3D static electric field finite element model of circuit breaker is established in ANSYS.Next,representative overvoltage conditions of AC filter is analyzed,the component voltage and transient stress of arrester under all the representative conditions are theoretically analyzed and calculated by simulation.Most serious condition of all types of AC filter arrester are put forward.Then,based on the above calculation results,insulation level of equipment and protection level of arrester are examined,and the optimized deploying scheme of frequently acted arresters are proposed.At last,the single break voltage of AC filter circuit breaker 5-10 ms after current interruption,that is the frequent accident period,is theoretically analyzed and calculated by simulation.At the same time,the regular pattern of electric field strength distribution of SF₆gas within the chamber is simulated and analyzed in ANSYS,the maximum electric field strength point is found,and the insulation characteristics of AC filter circuit breaker are comprehensively evaluated.