热老化下双层聚酯薄膜的冲击击穿特性

Impulse Breakdown Characteristics of Two-layer Polyester Films Under Thermal Aging

冲击电压作用下,干式空心电抗器的匝间绝缘失效问题时常发生,但其击穿机理尚不清晰。为此以热老化处理(80℃、130℃)的双层聚酯薄膜(PET)为研究对象,通过等温松弛电流法(IRC)分析介质归一化陷阱深度的变化规律,并对其介电特性和冲击击穿特性展开研究。通过建立固体电介质中束缚态电荷受迫振动过程中吸收能量的频率依赖模型,对热老化介质冲击特性的演变机理进行数值分析和计算。试验结果表明:两种老化温度下,随着老化时间的增加,介质的归一化陷阱深度先增加后减小,介质损耗正切tanδ在高频区域逐渐下降,而冲击击穿场强逐渐上升。数值计算表明:热老化过程中,介质归一化陷阱深度的增加和介质损耗正切tanδ的降低都有利于提升介质的冲击击穿场强。

The insulation failure of turn-to-turn insulation of dry-type air-core reactors under impulse voltages frequently occurs,but the mechanism of dielectric breakdown is still unclear.In this paper,samples of two-layered polyester film aged at different temperatures were prepared,and the variation of normalized trap depth of samples was analyzed by the isothermal relaxation current(IRC)method.Moreover,the dielectric properties and impulse breakdown characteristics of samples were studied.By establishing a frequency-dependent model of absorbed energy during the forced vibration process of trapped charges in solid dielectrics,the impulse breakdown characteristics were numerically analyzed and calculated.The experimental results show that,with the increase in aging time,the normalized trap depth of the dielectric increases first and then decreases,the dielectric loss tangent tanδgradually decreases in the high frequency region,and the impulse breakdown field strength gradually increases.Numerical calculation shows that,during thermal aging,the increase in the normalized trap depth and the decrease in the dielectric loss tangent tanδare beneficial to the increase of the impulse breakdown field strength.