高频电应力下温度对复合绝缘界面局部放电特性的影响机制

Influence Mechanism of Temperature on Partial Discharge Characteristics of Composite Insulation Interface Under High Frequency Electrical Stress

界面气隙空腔是引发固态变压器复合绝缘局部放电的重要原因。为厘清高频电场下温度对气隙空腔局部放电特性的影响机制,该文搭建高频电–热耦合应力下复合绝缘局部放电测量平台,开展不同温度下环氧树脂–聚酰亚胺复合绝缘气隙空腔的局部放电特性研究。结果表明:实验温度由30℃升高至180℃时,局部放电起始电压降低38.9%,平均放电幅值由35.2mV增加至171.9mV,单周波放电次数由50次/s增加至268次/s;相同温度下,放电幅值随频率增加而逐渐减低,放电次数则表现出增大。进一步给出温度对复合绝缘局部放电特性的影响机制:温升可提高电荷在界面处的迁移速度,降低气隙空腔内部合成电场,导致放电次数和放电幅值增加。该研究可为固态变压器复合绝缘状态检测提供一定的依据。

The air gap cavity at interface is an important cause of partial discharge in solid state transformer(STT)composite insulation.In order to clarify the influence mechanism of the temperature on PD characteristics of air gap cavity under high-frequency electric field,a set of composite insulation partial discharge test platform under high frequency voltage is established.The PD characteristics of the epoxy resin-polyimide composite insulation interface are investigated under different temperature.The results show that when the experimental temperature of composite insulation increases from 30℃to 180℃,the PD inception voltage decreases by 38.9%,the average discharge amplitude and the number of one-cycle discharge increase from 35.2mV and 50 times/s to 171.9mV and 268times/s,respectively,while the discharge repetition rate also increases from 50 times/s to 268 times/s.At the same temperature,the discharge amplitude decreases with the increase of voltage frequency,while the discharge times increase.It is revealed that the influence mechanism of temperature on PD characteristics of composite insulation is as follows:the temperature rise will improve the migration speed of charge at the interface and decrease the synthetic field distortion in the air gap cavity,which increase the number of discharges and the discharge amplitude.This paper provides a basis for the detection of composite insulation state of SST.