变压器倍频感应加压的电压测量研究

大型电力变压器局部放电和感应耐压试验采用倍频方式加压,当其激磁电抗不能补偿绕组杂散电容时,试品转为容性负载,试验回路存在容升现象,超高压、大容量变压器的容升问题尤为突出.本文引入容升因子分析容升的严重程度.试验时通常在变压器低压侧并联电抗器以降低试验系统容量,调节并联电抗器补偿度可在一定范围内调节容升因子.若在低压回路使用外接分压器校核回路变比,拆除分压器将导致回路容升因子的变化,一定条件下会产生很大的测量误差.研究表明,通过在高压套管末屏串联标准电容而构成分压器是解决这一问题简便有效的方法.

Study of Voltage Measurement During Induced Overvoltage Withstanding test of Transformers

When the withstanding voltage test is performed on transformers, a high voltage at a frequency more than two times the rated value is inductively applied on the HV windings. If the transformer behaves as a capacitive load, a capacitive rise exists, especially for EHV. In this paper a factor, named as the capacitive rise fact, is introduced to assess the rise. The factor can be adjusted to some extent by varying the reactance which has been connected to the LV side of the testing circuit to lower the capacity of the circuit. However, the factor changes when the voltage divider on the LV side is removed after the low/high voltage ratio has been calculated, and great error is resulted in under unfavorable conditions. A simple and effective way to avoid the problem is to connect a standard capacitance to the tap of the HV capacitive bushing of the transformer.