Taking the "7.13" fault of ± 800 kV Yibin-Jinhua DC project as an analysis object

we established a simulation model by using the power system analysis software MATLAB Sim Power Systems. The internal overvoltage characteristics and distribution of the grounding circuit of the UHVDC system were analyzed and the grounding line internal overvoltage level was quantitatively calculated. The analysis shows that the overvoltage inside the UHV grounding circuit depends on the grounding line length

system operation mode

and outgoing arrester parameters. The maximum internal overvoltage amplitude of grounding line is 278 kV on Yibin station side and 60 kV on Jinhua station side. The dry arc distance of grounding line shunt protective gap on Yibin station side was set to 20 cm

which causes failure of insulation coordination at "7.13" accident.