Study of Switching Overvoltage for Metallic Return Line of ±500kV Flexible HVDC Transmission Project

Abstract

For the flexible DC power grid, there is a complex electromagnetic coupling relationship between the pole line and the metallic return line when the line ground fault occurs. There is also a coupling between the different circuits. Metallic return line will produce switching overvoltage due to static and electromagnetic induction. Taking ±500kV Zhangbei flexible DC transmission project as an example, in the situation of monopolar grounding fault and DC circuit breaker failure clearance and then reclosing, the operation overvoltage on their own metallic return lines and adjacent metallic return lines in this progress are analyzed in this paper. The calculation results indicate that, the maximum overvoltage on the metallic return line is caused by its own pole line ground fault, which is not the transfer overvoltage. And the arcing horn gap values of metallic return lines at different altitude are concluded, which provide the parameters for the design and operation.