The presence of an insulation shield creates another problem. The grounded insulation shield results in the entire voltage stress being placed across the insulation. There is concern about exceeding the maximum stress that the insulating layer can withstand. The problem is magnified by stranded conductors or burrs and scratches that may be present in both stranded and solid conductors.
A semiconducting layer can also be added over the conductor to smooth out irregularities.
This reduces the probability of protrusions into the insulating layer. Protrusions into the insulating or semiconducting layer increase the localized stress. This stress may exceed the long-term breakdown strength of the insulation. This is particularly critical in extruded dielectric insulations. Any damage will be progressive and may lead to a total breakdown of the insulating layer