交叉互联电缆泄漏电流的分离及相间介损相对变化监测应用

Separation Method of Leakage Current in Cross-bonded Cables and Its Application in On-line Monitoring Relative Change of Dielectric Loss Between Phases

交叉互联电缆系统中介损监测存在两大难点,一方面交叉互联接线方式和同轴电缆的使用使得泄漏电流和护层电流的分离复杂,另一方面电压信号获取困难且对同步精度要求高。为此,建立了交叉互联电缆系统的等效模型,提出了泄漏电流与护层电流分离法,改进了交叉互联相间介损相对变化的在线监测方法而无需参考电压信号。在武汉某电缆隧道安装了电缆在线监测装置,以2014-12、2015-03和2015-05结果为例,三相结果基本满足I2BA>I2AC>I2CB的关系,表明B2段电缆相对变化程度比A2和C2段更快,其中2014-12—2015-03相间泄漏电流变化程度最大为0.89%,相间泄漏电流变化程度均<1%,未发现明显老化现象,与该段线路的环流和局部放电在线监测装置监测结果一致。

In on-line monitoring dielectric loss of cross-bonded cables, the main challenge is the interconnectedness of metal sheath and the application of coaxial cable in joints, which is hard to differentiate the leakage currents and sheath currents. Another challenge is that the reference voltage is hard to obtain synchronously with high accuracy. Consequently, we established an equivalent circuit model of cross-bonded cable system, and proposed a method to differentiate leakage currents and sheath currents. On-line monitoring method for relative change of DL was improved to diagnose the relative aging degree of cable insulation in the absence of reference voltage. An on-line measurement system was installed in a cable tunnel in Wuhan. In December 2014, March 2015 and May 2015, the results could satisfy the relationship 12BA〉I2Ac〉I2cB, and it was found that the variation of insulation condition in section B2 changed more than that in A2 and C2. The maximum relative change of leakage current between December and March was 0.89%, and each relative current change during the monitoring period was less than 1% without obvious aging. The results are consistent with the circulating current and partial discharge monitoring results.