Electrochemical effects at the conductor/dielectric interface - a description of the mechanism

If water is present in the conductor area in cables where an aluminium conductor is used, porous channels can develop in the inner semiconductive layer when exposed to accelerated aging. These porous channels may then initiate and promote growth of vented trees. The development of these channels was investigated by ageing model insulation systems in an accelerated test by use of various materials and ageing parameters. The causes for this electrochemical ageing mechanism have previously been reported; these are further discussed in this paper.