基于接地电流的交叉互联箱故障诊断技术研究

Fault Diagnosis of Cross-bonded Box Based on Grounding Current

为有效评判交叉互联箱内同轴电缆断裂、三相换位失败、进水三种故障,文中以实际运行线路为参考建立电缆线路模型。通过计算首端接地电流,提出了评判交叉互联箱内典型故障的诊断参数,分别为电流系数K和不平衡系数J。结果表明,箱内同轴电缆断裂时,故障相K值为0,非故障相K值小于1;三相换位失败时,两个K值大小几乎相等且接近正常工况标准值1,一个K值增加为正常情况下的2倍左右;箱内进水时,一箱、两箱进水时的K值较正常情况无明显变化,但J值差别较大,一箱进水的J值要显著大于两箱进水情况。该评判准则的建立以监测电缆系统首端接地线电流为基础,准则中采用的两个参数能够有效诊断全线交叉互联箱内典型故障,且两个参数避免了因负载电流、接地电阻等因素变化的影响。文中提出的方法简单、易操作、准确度高,可推广至长线路。

To efficiently evaluate three faults of coaxial cable breakage,unsuccessful three phase transposition and water ingress in the cross-bonded box,a cable line model is established according to the actual operating line. Current modulus K and unbalance coefficient J are presented by calculating the grounding current. They are used as evaluation parameters for evaluating typical faults in the cross-bonded box. It is shown that when the coaxial cable is ruptured,the value of K of faulty phase is 0 while the value of non-faulty phase is smaller than 1. When three phase transposition is unsuccessful,two values of K are almost equal and close to standard value 1,but the other value of K is about one time higher than the value of the normal condition. When wateringress happens in the cross-bonded box,the value of K does not change obviously,but the value of J for water ingress in one box is much bigger than that for water ingress in two boxes. The evaluation criterion is on the basis of monitoring the current in grounding line at the starting position of cable system. These two parameters of the criterion can be used to effectively diagnose the typical faults in the cross-bonded box on whole line without the influences of the changes of load current and grounding resistance. This diagnostic method is simple,easy to operate,and highly accurate,and it can also be applied to a long cable system.