The real operation experiences of the cross-linked polyethylene（XLPE） power cable show that the interface between the cable insulation and the joint insulation is the most prone to fail. Consequently

we investigated the effects of moisture on the initial discharge voltage

breakdown voltage

repeated pressure times

and carbonization degree of the composite interface of a cable joint in view of the XLPE cable joints. The experimental results show that

under dry condition

the interface flashover is unrecoverable; once the flashover occurs

test voltage can not be applied on specimens anymore; insulation can be recovered after surface flashover occurs due to moisture

namely

test voltage can be applied on specimens repeatedly; with the increase of repeated times

the initial discharge voltage decreases

while the average discharge current increases. The research results show that

under wet conditions

there exists an accumulation effect of carbonation damage at an interface material

and the final breakdown of interface is caused by gradually deeping the degree of carbonation at interface after flashover until going through the electrodes.