Ageing and diagnostics in extruded insulations for power cables

There are several polymers being used as extruded insulation in high-voltage power cables from 5 kV up to 500 kV. They include low density polyethylene (LDPE), crosslinked polyethylene (XLPE), tree-retardant crosslinked polyethylene (TRXLPE) and different formulations of ethylene propylene rubber (EPR). The ageing mechanisms of extruded insulations operating under wet (usually for medium-voltage cables) and dry conditions (for high-voltage cables) have been discussed. Diagnostic techniques, both destructive and non-destructive, have also been discussed using the possible ageing mechanisms as a basis.