Flashover Characteristics of Roof Insulator on High-Speed Trains Under Heavy Rain Conditions

Under heavy rain conditions, insulators are prone to local discharges, and roof insulators on high-speed trains, due to their compact design, are particularly susceptible to local discharges and even flashovers, posing a significant threat to train safety. Therefore, investigating the rain flashover characteristics of roof insulators is crucial. This article conducts artificial rain flashover tests on three common types of roof insulators, analyzing the effects of rainfall rate, rainwater conductivity, and insulator shed structure on their flashover characteristics. Meanwhile, finite element simulations model the descent of raindrops on the insulator sheds, investigating how the dripping, breaking, and bridging behaviors of raindrops between sheds affect the surrounding electric field distribution. The results indicate that the flashover voltage of the roof insulators decreases in a negative power exponential relationship with increasing rainfall rate and rainwater conductivity. The shed structure significantly affects the flashover characteristics, with discharges primarily occurring between sheds and along the shed edges. Multiple shed discharges may occur simultaneously, with smaller shed gaps increasing the likelihood of discharges. Raindrops falling along the shed edges can create tip effects and bridging effects, causing the maximum electric field strength to reach 89.91 kV/cm, which intensifies intershed discharges and guides the discharge paths.