极性反转电压下变压器油的击穿特性

Breakdown characteristics of transformer oil at DC polarity reversal voltage

为了获得换流变压器中变压器油在极性反转电压下的击穿特性,使用一种三电极模型,在不同间隙和温度下,对变压器油隙进行了极性反转电压击穿实验研究。击穿结果表明:极性反转电压下,变压器油的击穿场强没有随油间隙增加而降低;变压器油的击穿场强与温度相关,在实验温度范围内,40℃时出现了最大值。监测流过油隙的电流,发现在极性反转后电流变化曲线出现了随温度明显变化的暂态过程。针对传统液体电导理论不能对实验结果进行解释的问题,提出一种离子运动模型,利用该模型对极性反转电压下电流和电场变化进行分析,得到的电流和电场畸变引起击穿的特点与实验结果相一致,证明了该模型的正确性。

DC polarity reversal voltage breakdown experiments on transformer oil gaps by a three-electrode model under different gaps and temperatures are carried out in order to get polarity reversal voltage breakdown characteristics of transformer oil in the converter transformer.Breakdown results indicate that the breakdown field strength of the transformer oil does not reduce with the increasing of oil gap,and the strength is correlated with temperature and reaches the peak value at 40℃ within the range of experiment temperatures.Currents through those oil gaps are monitored and a transient process in which current varing curve changes obviously with the temperature appears after polarity reversal.The traditional liquid conduction theory can not explain the above results,so a model of ions moving is presented which analyses the currents and varies of electrical fields at polarity reversal voltage.Currents characteristics and breakdown characteristics caused by electrical distortion is in consistent with experimental results.Thus,it is proved that this model is correct.