Flashover Characteristics Of Roof Insulator In High-speed Charged Sand Environment

With the increasing train speed and the development of “eight vertical and eight horizontal” high-speed railway network in China,the design of high-speed trains needs to take into account the effects of extreme weather in all regions of the country.Frequent sand-dust weather in Northwest China has a major impact on the high-speed trains running on Lanzhou-Xinjiang railway.There are charged sand grains in wind-blown saltation.The original electric field of the roof insulator installed on the top of the high-speed train will be distorted when the high-speed train runs in the charged sand environment.As a result,the insulation performance of the roof insulator is influenced which threatens the safe operation of the high-speed train.At present,the research about the influence of wind-sand environment on insulator mainly focuses on power system,but there are few reports about the influence of high-speed charged sand environment on the flashover characteristics of the roof insulator.Therefore,it is of great significance to study the flashover characteristics of the roof insulators in the high-speed charged sand environment to ensure the safe operation of high-speed trains in areas with frequent dust storms.In this paper,charge-mass ratio measurement device of dust was designed based on the artificial experimental wind-tunnel platform.The dust environment on Lanzhou-Xinjiang railway was simulated by high-speed charged sand environment simulator.Research objects were needle-plate electrode,plate-plate electrode and epoxy resin insulator.The experiments about gap breakdown and insulator flashover were performed in pure high-speed airflow,high-speed sand and high-speed charged sand environments.The influence rules of wind speed,sand grain size,charge-mass ratio of sand on the gap discharge characteristics and insulator flashover characteristics were obtained.The mechanisms of the effect of the high-speed charged sand environment on the breakdown voltage and flashover voltage were lucubrated.Through a number of tests,it was found that the breakdown voltage and flashover voltage curves in pure high-speed airflow,high-speed sand,high-speed charged sand environment declined in turn.The electric field distribution was changed by sand grains and charge sand grains which made the nonuniformity of the electric field increase.As a result,the breakdown voltage and flashover voltage reduced.the voltages decreased with the increase of charge-mass ratio of sand.The breakdown voltage increased with the increase of the gap distance.Sand grains had an obvious promoting effect upon the development of discharge channel,and the degree of promotion increased with the increase of sand grain size.What’s more,the promotion would be further strengthened when sand grains were charged.The influence of wind speed on gap breakdown voltage varied greatly due to the unevenness of electric field.The effect of wind speed on the flashover voltage of insulator was similar to that of needle-plate electrode.These research results can provide reference for design and protection of roof insulators in high-speed charged sand environment.