选相投切对特高压变压器操作冲击绝缘的影响分析

Analysis of impacts of controlled switching on switching impulse insulation of UHV transformer

基于特高压断路器的电场强度分布给出了合闸预击穿时间的均值和标准差,再利用ATP-EMTP软件对空载变压器进行合理建模,并进行不同剩磁情况下的电磁暂态仿真,对考虑预击穿和机械分散性影响下的操作过电压进行了统计分析。同时,对最佳相位合闸时产生的励磁涌流进行了分析讨论。结合低压模拟实验的最终分析表明:即使考虑断路器预击穿、机械分散性以及励磁涌流的变化后,选相投切技术仍具有抑制过电压的作用,再结合避雷器可将过电压完全限制在标准要求值内。根据GB/Z24842—2009标准给出了变压器操作冲击绝缘水平的推荐值,可供工程设计参考使用。

Based on the electric field intensity distribution of UHV circuit breaker,the mean and standard deviation of the pre-breakdown time are given. Then the ATP-EMTP software is used to model the no-load transformer reasonably,and the electromagnetic transient simulation is carried out under different remanence conditions,and the switching overvoltages are statistically analyzed with the consideration of the influences of pre-breakdown and mechanical dispersion. At the same time,the inrush current generated during the optimal phase closure is analyzed and discussed. The final analysis of the low-voltage simulation experiment shows that even considering the pre-breakdown,mechanical dispersion and the change of inrush current,the controlled switching technology still has the effect of overvoltage suppression,and combining with the arrester the overvoltage can be completely limited within the standard requirements. Finally,according to the standard GB/Z24842—2009,the recommended value of switching impulse insulation level for transformer is given,which can be used for engineering design reference.