低气压下绝缘子串直流污闪放电模型及验证

DC Pollution Flashover Model and Its Validation of Polluted Insulator Strings Under Low Air Pressure

为揭示低气压下染污绝缘子串闪络机理,并为低气压地区外绝缘选择和设计提供参考,在人工气候室模拟低气压条件,以7片串XP-160绝缘子为例,进行了不同低气压、污秽下绝缘子直流放电特性试验研究,并拍摄了其放电过程。试验结果表明:低气压下直流污闪放电过程中局部电弧存在飘弧现象,因此提出低气压下染污绝缘子串直流放电过程的电路模型是由剩余污层电阻、沿面电弧和空气间隙电弧串联组成;根据模型计算所得的临界污闪电压与实测值的误差在10%以内;揭示了静电力和热浮力随气压变化规律的差异是低气压下局部电弧发展中飘弧现象更严重的主要原因。

To reveal the flashover mechanism of polluted insulator strings and to offer some consult for the external insulation selection and design under low air pressure,a series of tests were carried out in the low air pressure condition simulated by artificial climate chamber.Taking 7 units of XP-160 for examples,we experimentally researched the DC discharge performance of insulator at different low air pressure and pollution degree in which the discharge process was taken by high speed vidicon.The experimental results show that some of the partial arcs may deviate from the surface of insulator string and form the air gap arc during the DC pollution flashover discharge process under low air pressure.So a circuit model explaining the DC discharge process of polluted insulator strings under low air pressure is given,which consists of a surface arc,air gap arc and residual resistance of the pollution layer.The relative error of critical pollution flashover voltage got by the model and the experimental results is lower than 10%.The results reveal that the difference between influences of air pressure on electrostatic force and thermal buoyant force is the main reason which makes the partial arc deviated from the surface of insulator more severely under low air pressure.