低温环境对环氧树脂电气性能的影响

Influence of Low-temperature Environment on the Electrical Properties of Epoxy Resin

高压直流电缆运行于极寒地区时,其电缆接头环氧树脂绝缘件通常会面临极端的低温环境。为探究低温环境对环氧树脂电气性能影响,对环氧树脂在−20、−40和−60℃下分别开展7、15和30 d的低温处理试验后,对其直接进行微观结构表征及直流电气性能测试,并研究了低温环境对环氧树脂电气性能影响机制。结果表明,随着低温处理时间增加,环氧树脂表面会出现微裂纹并不断劣化,而其直流击穿强度和电阻率均呈现先上升后下降的趋势,并且这种变化趋势随着处理温度的降低愈加明显。而将−60℃不同低温处理时长的环氧树脂室温放置3个月后再进行测试,则其击穿强度相较于未经低温处理直接室温放置3个月的试样显著下降。分析认为,这种现象是由微裂纹和自由体积共同作用引起的,环氧树脂电气性能上升主要是由低温下自由体积减小引起的,而电气性能下降则是微裂纹导致的。

When HVDC cables operate in freezing areas,the epoxy insulation of cable connectors is usually exposed to extremely low temperatures.To explore the influence of a low-temperature environment on the electrical properties of epoxy resin,epoxy resin samples were treated at−20,−40,and−60℃for 7,15 and 30 days,respectively.Then,the treated epoxy resin samples were characterized physically,and the DC electrical properties,such as breakdown strength and resistivity,were researched.Moreover,the influence mechanism of the low-temperature environment on the electrical properties of epoxy resin was researched.The results show that the microcracks will gradually appear on the surface of epoxy resin and continue to deteriorate with the increase of the treatment time.The DC breakdown strength and resistivity of epoxy resin show a trend of increasing first and then decreasing.This trend becomes more significant with lower treatment temperatures.However,compared with the sample placed at room temperature for three months without low-temperature treatment,the breakdown strength of the epoxy resin placed at room temperature for three months after low-temperature treatment decreases significantly.This phenomenon is caused by the combined effect of microcrack on the surface of epoxy resin and free volume in it.The improved electrical properties of epoxy resin are mainly caused by the decreased free volume in low-temperature environments.In comparison,the degradation of the electrical properties is caused by microcracks.