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Microcavity on Tracking Failure of XLPE-SiR Interface

Micro-cavity may possibly be introduced into the XLPE-silicon rubber interface in installation of XLPE cable joint. This type of defect greatly decreases the interfacial breakdown strength and endangers the stability of power system. However, the tracking failure process is still unknown. In this paper, three types of interfaces with different dimension of micro cavity were setup by pressing together a slice of XLPE and a slice of transparent silicon rubber. A 50 Hz AC voltage source was applied on a pair of flat-round electrodes which was sandwiched at the interface with their insulation distance of 5 mm until tracking failure. The discharge light from discharge to the failure at the XLPE-SiR interface of artificial cable-joint was detected and analyzed to reveal the micro cavity on the failure of cable joint. Obtained results show that micro cavity at an XLPE-SiR interface easily leads to interfacial discharge and failure. A longer cavity more easily leads to interfacial discharge and failure than a shorter one. It is helpful in approximately analyzing the failure mechanism of XLPE-SiR cable joint.