电缆半导电屏蔽层中导电离子析出模型分析

Model Analysis of the Conductive Ions Escaped from the Cable Semi Conductive Shield

中低压电力电缆主绝缘的水树现象是造成电缆故障的一个很重要的因素,在温度和高电场等外界条件共同作用下,电缆半导电屏蔽层中含有的游离导电离子析出后在电缆主绝缘表面形成水树现象的起始点。通过对半导电屏蔽试样水煮得到的数据进行分析,建立扩散模型,利用Fick第二扩散方程对该模型进行解析,得到t时刻试样中导电离子的浓度分布并与导电离子的析出试验数据相符。

Water treeing in the primary insulation is a very important failure mechanism for lower and medium voltage cables. Under the joint effect of operation temperature and high electric field, the free conductive ions will escape from ＂the cable semi conductive shield and form the inception of water treeing in the primary insulation. A diffusion model was established based on the data obtained from boiling of the semi conductive shield sample. Fick＇ s second diffusion equation was sued to analyze the model. The resulting distribution of conductive ions concentration in the sample at time t with agreed with the result of the test for conductive ions escape.