Current Distribution of Multi-column Parallel Metal Oxide Voltage Limiter

Metal oxide voltage limiter (MOV), as an important part of series compensation device (series complement device), is used to limit the transient overvoltage between capacitor electrodes when the system fails. MOV is generally composed of multiple units in parallel to absorb huge energy in the event of failure, to pass large current and absorb high energy at the moment of MOV protection action, so the consistency of MOV parallel unit operation characteristics and uniform distribution of transient current are important guarantees to ensure the safe operation of MOV. This paper takes the practical project of Luoping-Baise and Mawo-Baise 500kV series complement transmission system of China Southern Power Grid as the research background, establishes the numerical simulation model of series complement transmission system according to the V-A characteristics and volt-temperature characteristics produced by mainstream MOV companies in China, and according to the current distribution coefficient of actual MOV unit allocation. It is concluded that when considering the MOV transient temperature characteristics, the maximum absorbed energy of MOV units with minimal local impedance is directly proportional to the current distribution coefficient between MOV units and the temperature difference before secondary failure, and inversely proportional to the single-phase MOV absorbed energy margin. Based on the simulation results, several measures to optimize the transient load stress distribution among multiple MOV units are proposed.