双指数及振荡型操作冲击电压下变压器匝间击穿特性

Breakdown Characteristics of Transformer Turn-insulation Under Double-exponential and Oscillating Switching Impulse Voltage

据国家电网系统变压器故障情况统计,绕组匝间绝缘失效是导致变压器故障的主要原因。因电路投切产生的操作冲击电压威胁着变压器内部的匝间绝缘,并可能导致匝间绝缘击穿。操作冲击耐压试验对检验变压器绝缘性能具有重要的工程价值。本研究在变压器匝模型上分别施加双指数操作冲击电压以及3 kHz、6 kHz、12 kHz振荡操作冲击电压,通过多级法进行试验,并根据伏秒特性、韦伯分布曲线研究其击穿特性。研究结果表明:4种操作冲击电压的击穿点主要分布在第1个波峰附近,6 kHz以及12 kHz振荡操作冲击电压在第2个波峰附近有少量分布;相同波前时间的双指操作波以及3 k Hz振荡操作波的等效性较好;振荡操作冲击波的击穿电压随着频率的增大而增大;3~6 kHz频率范围内,振荡操作波与双指数操作波U50%接近,等效性较好。

According to the statistics of transformer faults in the National Grid System, the failure of winding turn-to-turn insulation is the main reason for transformer faults. Switching impulse voltage generated by the circuit switching threatens the transformer winding, and further may lead to insulation failure of the transformer turns. The switching impulse withstand test is important for the transformer insulation test and is meaningful for engineering. In this paper, double-exponential switching impulse voltage and 3 k Hz, 6 k Hz, 12 k Hz oscillating switching impulse voltage are respectively applied to the transformer turn-insulation model, and the test is carried out through the multi-stage method.Moreover, the breakdown characteristics are studied through the volt-second characteristic and the Weibull distribution curves. The research results show that the breakdown points under the switching impulse voltages are mainly distributed near the first wave peak. 6 kHz and 12 kHz oscillation switching impulse voltage have a small distribution near the second peak. The double-exponential switching impulse voltage and the 3 kHz oscillating switching impulse voltage which have the same wave front time are more equivalent. The breakdown voltage of the oscillating switching impulse voltage increases with the increase of frequency. In the frequency range of 3~6 kHz, U50% under the oscillating switching impulse voltage is close to that under the double-exponential switching impulse voltage, and their insulation equivalence is better.