复合绝缘子HTV硅橡胶材料老化特性的研究

Influence of Corona Discharge on Aging Characteristics of HTV Silicone Rubber Material

针对在役复合绝缘子的老化问题,笔者分别对实验室电晕老化和现场自然老化的HTV硅橡胶材料的憎水性、泄漏电流、表面微观形貌以及化学成分等特性进行了对比研究。结果表明,电晕老化与现场老化造成材料特性变化的规律呈现一致性:电晕老化造成材料憎水性下降,且提高电晕老化强度(电压和时间)则导致憎水性恢复变慢,甚至不能完全恢复;现场老化材料的憎水性随年限不断下降,由HC1级(2年)降至HC5级(15年)。老化还造成样品的表面电阻率下降,引起表面泄漏电流增加;老化造成硅橡胶材料降解,表面缺陷增加,孔洞增加并加深,甚至产生裂纹,同时生成强极性基团等,从而引起硅橡胶机械及绝缘性能不断下降。

To obtain dominant parameters of material characteristics for evaluating aging state of composite insulators effectively, a comparative study was performed on the HTV silicone rubber material aged by corona discharge in laboratory and by natural environment, in regard to such parameters as hydrophobicity, surface leakage current, surface microstructure and chemical composition. Experimental results show that the characteristic parameters of the silicone rubber material under two kinds of aging conditions exhibit similar change rules. Corona aging condition decreases hydrophobicity, and increasing corona voltage or acting time leads to a sharper drop and a slower recovery or even uncompleted recovery in hydrophobicity. Hydrophobicity decline is also observed in the naturally aged specimens from HC1 level in two years to HC5 level in 15 years. In addition, surface resistivity also decreases with aging time and thus surface leakage current increases. SEM and FTIR analyses show that both corona aging and environment aging conditions induce increasing surface defect density and deepening pits, and even cracks. Moreover, aging gets the molecular chain of silicone rubber material broken and results in the generation of strong polar groups, worsening the mechanical