电力电缆线性高阻击穿故障的特点及定位方法

交联聚乙烯和聚氯乙烯绝缘电力电缆的大量应用中,出现了一种新型的高阻击穿:其等效电阻相当稳定,用兆欧表500 V至5000 V档测量,击穿点绝缘电阻几乎不变,该类击穿点也许不能承担高电压,但很难降低其电阻,即使施加高压脉冲也无法击穿,因此难以通过脉冲电流法,乃至二次脉冲法、三次脉冲法定位。该类高阻击穿故障被定义为线性高阻击穿故障,是目前公认的定位难点。本文详细讨论其形成的原因,定位方法等。结论是:线性高阻击穿可以使用高压定位电桥直接定位;或通过合适的烧穿源降低绝缘电阻,再使用电桥或波反射法定位,关键是烧穿源必须有足够高的电压及功率。

Characteristics of the Linear High Resistance Breakdown Fault in Power Cables and its Location

In the widespread application of XLPE and PVC power cables,a new high resistance breakdown fault is found,which has the features as follows.The equivalent resistance is rather stable.The insulation resistance at the breakdown spot remains almost unchanged when measured by Mega-ohmmeter at 500 V～5000 V.The breakdown spot,which may not with-stand high voltages,has a resistance that is hard to be lowered and cannot be broken through even by application of HV impulses.Thus it is not possible to locate such fault by the pulse method,even by the double and triple pulse methods.This high resistance breakdown fault is defined as the linear high resistance breakdown fault,a recognized hard-to-locate fault.This paper presents the formation of the fault and the method to locate it.The author concluded that the linear high resistance breakdown fault can be located directly by the HV location bridge or located by the bridge or echo meter after decreasing its resistance by burning(it is of key importance that the burning source has sufficiently high voltage and power).