Research on Induced Voltage and Current for Hybrid Transmission System Composed of GIL and Overhead Line

Abstract Gas insulated metal-enclosed transmission line (GIL) is a substitute for overhead line, which is used for power transmitting in complicated geographical or geological environment In order to satisfying the requirements of operation in maintained state, each side of GIL needs to be installed a grounding switch. For the hybrid transmission system composed of GIL and double-circuit overhead line, the whole overhead line will be divided into incomplete transposed/non-transposed parts due to connection of GIL. When one of the grounding switches of GIL closes, it can lead to much greater induced current in each grounding switch. The induced voltage and current for hybrid transmission system will also change because of different parameters between GIL and overhead line. Calculation methods of induced voltage and current for hybrid transmission system with GIL are presented in this paper. Then, calculation conditions for hybrid transmission system are analyzed based on these evidences. Su-Tong GIL pipe gallery project is taken as an example for simulation in ATP/EMTP. Compared with traditional transmission system with overhead line, much higher performance requirements for grounding switches of Su-Tong GIL pipe gallery project are necessary, especially for induced current.