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 wound shield. Such conditions can lead to (i) the ground shield becoming effectively floating or (ii) the ground shield acting as a dielectric rather than a 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 that 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.