Threshold voltage for electrical tree inception in underground HV transmission cables

Experimental evidence is provided to show that irreversible aging which leads to electrical treeing in polymeric insulation such as low-density and crosslinked polyethylene used in HV transmission cables, does not start at local fields between 5 and 20 kV/mm. It is shown that a much higher stress is required for electrical tree inception and that the electroluminescence inception voltage is the threshold voltage at which the polymer starts to degrade.>