热老化对EPDM电树枝局放特性的影响研究

Study on the Effect of Thermal Aging on Partial Discharge Characteristics of EPDM Electrical Tree

电树枝生长过程中常伴随有局放发生,其与电树的发展有极大关系,并会导致绝缘出现不可逆的损伤。为此,在140℃下对三元乙丙橡胶(EPDM)绝缘试样进行了梯度加速热老化,并对不同老化程度试样开展了电树枝观测试验,采集了电树枝生长过程的局放信号,结合陷阱参数测试分析了热老化对EPDM电树枝局放特性的影响机理。结果表明:老化前期,电树枝发展表现为4个阶段,而老化后期为2个阶段;未老化EPDM电树枝放电相位分布在-50~90°与130~270°内,且正半周放电更剧烈;局放随电树枝的延伸同样呈现一定的阶段性变化,且随老化时间增加,放电量、放电次数与放电总能量先降低后大幅增加;陷阱测试显示,陷阱密度及能级随热老化时间先减小后增大,绝缘内部电荷聚集,对局放有极大影响。

The growth of electrical tree is often accompanied by the occurrence of partial discharge,which has a great impact on the development of electrical tree and leads to irreversible damage of insulation.For this reason,For this reason,the ethylene propylene diene rubber(EPDM)insulation samples were subjected to gradient accelerated thermal aging at 140℃.Electrical tree observation tests were carried out on samples with different aging degrees,and the partial discharge signals during the growth process of electrical tree were collected.Combined with the trap parameter test,the influence mechanism of thermal aging on the electrical tree partial discharge characteristics of EPDM is analyzed.The results show that:in the early stage of aging,the development of electrical tree has 4 stages,while the latter stage of aging has 2 stages.The partial discharge also shows a certain periodic change with the extension of the electrical tree.With the increase of aging time,the discharge amount,discharge times and total discharge energy first decrease and then increase significantly.The trap test shows that the trap density and energy level first decrease and then increase with the thermal aging time,and the charge in the insulation accumulates,which has a great impact on the partial discharge.