Simulation of secondary overvoltage of voltage divider for wall bushing in flexible direct current transmission system

Abstract Wall bushings used in Flexible Direct Current Transmission Systems are key equipment for achieving electrical connections between equipment inside and outside the valve hall, and the ground voltage of the bushings can reflect their operating status. However, there have been cases of damage to the secondary side of the voltage divider in engineering applications using the voltage measurement method of dividing the voltage at the end screen of the wall bushing, which is currently used as a monitoring method. This article first analyzes the structure of the bridge arm capacitive wall bushing and establishes a wideband equivalent circuit model for the wall bushing. Next, we integrate the wall bushing and voltage divider models with the wideband model of the Flexible DC Transmission System. We also simulate the overvoltage on the secondary side of the wall bushing voltage divider under the influence of electromagnetic interference sources during switch operation. The simulation shows that the overvoltage of the wall bushing secondary system is 4p.u, which exceeds the unit value of the voltage borne by the voltage divider.