特高压交流试验示范工程线路操作冲击试验电压波前时间计算分析

Simulating Calculation and Analysis on Time-to-crest of Switching Impulse for Test on Chinese UHV AC Pilot Project

为了利用特高压示范工程猫头和水平塔长波前操作冲击下线路空气间隙放电电压较标准操作冲击波高的特点,减小空气间隙距离,降低杆塔造价,需要确定特高压示范工程猫头和水平塔空气间隙操作冲击放电试验波前时间。根据国外非标准的操作波对空气间隙的放电电压影响的试验研究结果,推导了线路操作过电压的波前时间和等效操作冲击试验电压波前时间之间的换算关系,并计算了中国单回路特高压示范工程线路操作过电压波前时间及与之等效的操作冲击试验电压波前时间,统计分析了转换得到等效试验用操作冲击的波前时间与幅值的关系。采用统计法和简化法计算线路闪络率,指出虽然计算结果满足标准要求,但由于变异系数对线路闪络率影响很大,而变异系数随着波前时间的增大有一定提高,长波前操作冲击放电分散性较短波前大。因此兼顾安全和经济性,1000μs操作冲击用做试验冲击是合适的。

For UHV AC transmission lines,the sizes of tower windows are related to the air clearance determined by switching overvoltage.According to the air clearance switching-impulse（SI） test results obtained by China and other countries,longer the time-to-crest of switching impulse wave shape is,higher the discharge voltage of the air clearance is.To reduce the size of transmission line tower windows and save project construction cost,it is important to determine the time-to-crests of SI for test.We derived a conversion formula between waveforms of SOVs on transmission line and time-to-crests of SI for test,calculated the equivalent time-to-crests of SI of UHV transmission lines with EMTP,and analyzed the relationship between the equivalent time-to-crests of SI and amplitude of SOVs.Moreover,we calculated the flashover rate of transmission line by both statistic method and simplified method.The results can meet the requirements of national standard.However,the coefficient of variation affects the flashover rate greatly,and coefficient of variation of the 50% flashover voltage increases with the longer of the time-to-crest,namely,flashover voltages under long-time-to-crest SI have larger dispersion than those under short-time-to-crest SI,so 1000μs SI for air clearance SI test with cat-head-tower and cup-tower of UHV AC pilot project is suitable for impulse test considering the safety and cost.