Evaluation of field aged crosslinked polyethylene cables by partial discharge location

Partial discharge sites were located in several field aged crosslinked polyethylene insulated medium voltage power cables, using a newly developed instrument. Subsequent AC breakdown tests indicated that, with partial discharge inception voltages lower than 3 times operating voltage, the failures occurred at the partial discharge sites. In all cases, the failures originated at the sites of long water trees which affected the cables at discrete locations rather than uniformly over their entire lengths. Attributes of a partial discharge locator capable of performing in-situ nondestructive diagnostic tests on cables are discussed and field application procedures are described