Study On The Operating Condition Of500kV Series Compensation MOV

MOV（Metal Oxide Varistor）as primary protection is the most important device of seriescompensation. MOV restricts series compensation capacitor over-voltage using its stronglynonlinear current-voltage curves in order to ensure series compensation devices safe andreliable.Operation conditions of Series compensation MOV is hardly different from MOA (MetalOxide Arrester). MOV has large surge absorption capability and high level of frequencywithstand ability. For meet engineering and technical requirements, most of seriescompensation stations utilize multi-column parallel structure. Since2008, some500kV seriescompensation stations, such as BaiSe station, PingGuo station, HeChi station, YanShanstation, belong to China Southern Power Grid Company have MOV explosions or pressurereleasing actions, which seriously affected series compensation reliable operation and safetyof workers responsible for operation and maintenance of series compensation. After analyzingthe cause of accidents by MOV disintegration and test analysis, finding MOV without dampand manufacturing issues. Simulation and system debugging can indicate MOV has largecurrent flow capacity. Therefore, the capacity of frequency withstand of series compensationMOV or selection of MOV design parameters maybe result in MOV accidents.This paper carried out the study on operating condition of500kV series compensationMOV, concerned with the capacity of frequency withstand and flow capacity of MOV afterincrease of power frequency voltage resulted from single phase grounding fault andthree-phase grounding fault. Comparatively studying on the change rules of operatingcondition of500kV series compensation MOV and several factors, such as, systemshort-circuit capacity, series compensation ratio, overvoltage protection level, fault locationand fault type. In order to illustrate the relations between MOV condition and abovementioned influencing factors, this paper built typical500kV series compensation systemmodel using EMTPE according to C.S.G.500kV series compensation practical situation, andthen comfirmed gap triggering setting value determined by external fault, and calculatedinternal fault, and finally induced this change rules guiding design of series compensationsystem and selection of MOV.