Non-Contact Surface Metrology of Degraded Conductor Screens in XLPE Cables

Stress-induced electrochemical degradation (SIED) structures are likely initiated at the surface of the conductor screen of insulated XLPE cables with stranded aluminum conductors due to water ingress and corrosion. In time such structures initiate severe vented water treeing which significantly reduce the lifetime to the cable. The main purpose of this paper is to show that SIED structures are porous structures which swell and become visible after wetting in hot water, by using non-contact surface metrology characterization. It is found that after wetting SIED structures were imaged as elevations of water saturated porous structures. The swelling was less than 10 μm and could be permanent dependent on ageing conditions