Discharge Performance Of Long Air Gaps Under Low Air Pressure

In recent years,the China's electricity demand is growing rapidly with the development of power industry.However,the development of productive forces and energy resources are adversely distributed.The eastern region has developed productive forces,while the western region is rich in resources.Therefore,the use of long-distance,high-capacity transmission has become an inevitable trend.Due to the high average altitude in western China,so the construction of transmission and transformation engineering projects will inevitably go through different areas with high altitude.Air gap commonly used as the insulation medium in power system and electrical equipment.Therefore,the long air gap as the main way of external insulation,how to choose the air gap is important to the insulation design of power transmission engineering,the serious breakdown will occur if the external insulation design is inappropriate.In order to study the effects of rod tip shapes on the discharge characteristics of rod-plane gap under low air pressure,a test platform was set up.AC/DC discharge tests were carried out for conical tip,hemispherical tip,and flat tip three rod electrodes at 100?400mm of rod-plane gap and in 2?20kPa,and then the results of discharge characteristics test of different rod tips were verified through simulation.And taking the conical tip as an example,,the discharge characteristics of the rod-plate air gap under low atmospheric pressure were studied,The effects of P and d on U were analyzed in the range of 2 to 60kPa and put forward voltage correction for-mulas of AC voltage.Also,the effects of P and d on U were analyzed in the range of 2 to 30kPa and put forward voltage correction formulas of DC voltage.The results show that the rod tip shapes have significant impact on the discharge characteristics of rod-plane gap under low air pressure.With the increase of the air pressure,the U-P curves of all kinds of rod-plane gap show steady upward trend.As the increases of altitude,the P and U decreases,but there are some differences in the trend of U decrease in different air pressure range,The discharge voltage U under the AC voltage is less than positive polarity DC voltage U,and there are some differences in the development process of discharge channel.and the U correction formula based on the experimental data has a high accuracy.The results can provide reference for the study of the discharge characteristics of rod-plane air gap at high altitude and low pressure conditions,and the systemic discharge tests for rod-plane air gaps.