气体绝缘开关设备电缆终端绝缘硅油老化问题试验研究

Experimental Research on Ageing of Insulation Silicone Oil in Cable Terminal of Gas Insulated Switchgear

气体绝缘开关设备（GIS）高压充油电缆终端绝缘硅油随运行时间的增加会逐渐老化,从而造成电缆终端的绝缘性能大大降低。为了进行硅油老化状态的判定,首先研究了热老化对硅油电气性能的影响,然后采用针板电极对硅油进行了放电老化试验,通过不同放电形式下击穿电压、介质损耗角正切（简称介损值）、体积电阻率等电气参数的变化规律以及MALDI-TOF质谱分析的结果来评价硅油的老化状态。综合以上分析,证明了单纯的热老化对硅油电气性能的影响较小且非常缓慢,并且初步形成了硅油老化状态的评价标准：若击穿电压U≥40 kV,介损值tanδ≤0.6%,体积电阻率ρ≥5×1012Ω·m,质谱分析表明没有明显低分子量聚硅氧烷生成,则硅油处于轻微老化状态;若击穿电压U为30~35 kV,介损值tanδ为1%~1.5%,体积电阻率ρ为1011~1012Ω·m,质谱分析表明分子量在1 400~2 400范围内时出现稳定间隔吸收峰,则硅油处于中度老化状态;若击穿电压U≤25 kV,介损值tanδ≥5%,体积电阻率ρ≤1010Ω·m,质谱分析表明分子量在550~750甚至更低范围内时出现稳定间隔吸收峰,则硅油处于严重老化状态。

Insulation silicone oil in gas insulated switchgear （GIS） terminal of high voltage cable gets ageing gradually under longtime working, which will eventually degrade the overall insulation capability. To assess the ageing status of si- licone oil, firstly, we investigated the influence of thermal ageing on the electrical properties of silicone oil, then we experimentally create a needle-plane electrode system in which silicone oil would discharge by different forms. Through the changes of electrical parameters such as breakdown voltage, tangent of dielectric loss angle, volume resistivity, and MALDI-TOF mass spectral analysis, we could determine the ageing status of silicone oil. Finally, analyzing all these re- suits together, we can find that effect of thermal ageing on the electrical properties of silicone oil is very slow, then we present a preliminary evaluation criterion for ageing status of silicone oil： when breakdown voltage U≥40 kV, tangent of dielectric loss angle tanδ≤0.6%, volume resistivity ρ≥5× 10^12Ω.m, and mass spectral analysis shows that there is no ob- vious low molecular weight siloxane formation, then silicone oil is in the mild ageing condition; when breakdown voltage U=30-35 kV, tangent of dielectric loss angle tanδ=1%-1.5%, volume resistivity p=10^11-10^12 Ωm, and mass spectral analysis shows that in the range of 1 400-2 400 for molecular weight, absorption peak of stable intervals occurs, then si- licone oil is in the moderate ageing condition; when breakdown voltage U≤25 kV, tangent of dielectric loss angle tanδ≥5%, volume resistivity ρ≤10^10 Ω.m, mass spectral analysis shows that in the range of 550-750 or less for molecular weight absorption peak of stable intervals occur, then silicone oil is in the serious ageing condition.