Modeling and Prediction of Overvoltage Induced by Spark-Gap-Triggering in 500 kV Fixed Series Capacitors

In sparking over of bypass gap of 500 kV Series Capacitors (SC), fast-front transient overvoltage between low-voltage bus and platform is induced and may cause damage or malfunction of platform-mounted objects such as CTs, and protection and control devices. This paper aims at predicting the overvoltage of 500 kV Series Capacitors induced by bypass gap sparkover through modeling and simulation. The modeling method of Series Capacitors, including platform, buses, Metal Oxide Varistor (MOV), bypass gap, insulators etc. was demonstrated first. Second, bus-to-platform overvoltage as well as its distribution along bus length was calculated and predicted using SPICE. On mitigating the overvoltage level, suppression measure was adopted with effectiveness analyzed, and simulation results under different bypass gap dynamic conditions were presented. Lastly, several proposals based on simulation results were given to further control the overvoltage between low-voltage bus and platform to protect platform-mounted equipment from victimization.