Study on the influence of rainfall on the electric field distribution and switching impulse voltage of large-size sphere-plane gap

Previously, the research about the influence of rainfall on the discharge characteristics of the gap mainly focused on the severe non-uniform electric field gap such as rod-plane, rod-rod, or tower head of which the electrode size was generally small. As the DC voltage level increases, the size of the fitting at the end of the device further increases. As a result, the impact of rain on the discharge characteristics would have significant changes. In this study, the influence of rainwater on the electric field distribution characteristics of the sphere-plane air gap was simulated and the electric field distortion characteristic formed by the rain collected at the bottom of the fitting was obtained. Then, the impulse discharge test of the fitting under different rainfalls was conducted from which the influence of different rainfall on the impulse discharge voltage of sphere-plane gap was analysed. The research results can be used to optimise the design of the end fittings of outdoor DC field equipment.