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

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 I_2BA>I_2AC>I_2CB, 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.