Failure mechanisms of shielded power cable related to high ground shield resistance and/or insulation of neutral wires from the ground shield

A number of conditions can cause separation of the neutral wires from the semiconducting ground shield or cause a large increase in the resistivity of the ground shield. Such conditions can lead to i) the ground shield becoming effectively floating or ii) the ground shield acting as a dielectric rather than conductor. In either case, this can lead to partial discharge under normal operating voltage and/or lightning surge-induced flashover between the neutral wires and ground shield, conditions which can cause cable failure. The theoretical context of these conditions is examined, after which a concrete example which has resulted in field failures is provided.