Test Research on Heavy Rain Flashover Performance Improvement of Outdoor Insulation in EHV/UHV Substation

To understand the effect of water-cut sheds on flashovers of contaminated hollow core insulators in heavy rain,we performed simulative experiments.Taking 5-meter-long hollow core porcelain insulators for examples,we experimentally simulated flashovers on the samples in heavy rain,and measured the characteristics of the flashovers.Moreover,we analyzed the whole arcs propagating process,including the processes of initiating,developing,and flashover or withstand,under the test conditions,as well as the typical features of leakage current changes synchronously with arcs.The tests show that,with similar creepage distances,insulators in the presence of 4water-cut sheds and 8water-cut sheds have maximum withstand voltages averagely 72.7%and 127.3% higher than those in the absence of water-cut sheds,respectively.Adding water-cut sheds would influence insulator wetting,cut raining bridges and impede arcs from bridging,and it also accelerates leakage current growing from zero to maximum or turning into flashover.It is concluded that water-cut sheds significantly enhance the withstand voltage of bushing under heavy rain.The results also indicate that when bushings or post insulators are chosen for outdoor insulation,the creepage distance of equipment should not be the only criteria.