运行高压交联聚乙烯电力电缆的介电性能

Dielectric Properties of Operated High Voltage XLPE Power Cable

为探究高压交联聚乙烯(XLPE)电力电缆在运行一段时期后的绝缘性能变化表征及老化程度判别依据,对新电缆、实际运行年限为2 a、5 a、9 a和12 a的220 k V高压XLPE电缆绝缘的介质损耗因数频谱、氧化诱导期和工频击穿电场强度等进行了研究。对实际不同运行年限的电缆样本进行了轴向切片处理,制取了表面平整、厚度为1 mm的片状试样并进行了测试。试验发现:XLPE的低频介质损耗因数与老化程度存在对应关系,当频率在0.1 Hz以下时,介质损耗角正切值(tanδ)随老化程度而呈现明显线性上升趋势;随着运行年限的增长,XLPE电缆的氧化诱导期(OIT)与羰基指数这2项参数均同时增大;当运行年限达到约5 a和12 a时,XLPE电缆的击穿电场强度明显下降,运行年限为12 a电缆的击穿电场强度比新电缆的降幅可达约13%。对以上参数的测量都可以作为评估运行XLPE电缆老化状态的有效手段,其中测试运行XLPE电缆的绝缘击穿电场强度变化情况可以反映其综合老化程度,是适合于实际工程应用的简单有效方法。

Tests were conducted to find criteria for characterizing and evaluating the insulation performance and aging status of high voltage（HV） cross-linked polyethylene（XLPE） cables operated for a period of time. The objects included insulation samples harvested from 220 kV XLPE cables operated for 2, 5, 9, 12 years and a new cable, and these samples were made into axial slices with thickness of 1 mm and smooth surface. We tested the samples and measured their dielectric loss（tan δ）, oxidative induction time（OIT） and AC breakdown voltage. It is obtained that the low-frequency dielectric loss of XLPE cable is related to aging degree： for frequencies below 0.1 Hz, dielectric loss angle tangent value（tanδ） increases significantly with deepening aging level. Meanwhile, OIT and carbonyl index will increase with increasing operating duration. When the service time reaches 5 years and 12 years, the AC breakdown voltage significantly decreases ： for a cable in service 12 years, the AC breakdown voltage will be 13% less than that of a new cable. The measurement of these parameters can be an effective method for aging state assessment of XLPE cables in service. Meanwhile, testing the breakdown voltage of XLPE cable insulation can give general information of cable aging, and it is simple, effective and suits engineering practices.