High-Frequency Loss in Unjacketed Distribution Cable and Its Effect on PD Measurement

A cable jacket ensures intimate contact between neutral wires and the ground shield of the cable. For unjacketed cable, no such contact is ensured, and the loss caused by the ground shield is a function of the separation (capacitance) between the neutral wires and the ground shield as well as the distance between points of contact of the neutral wires with the ground shield. We have parameterized the loss as a function of neutral wire separation from the ground shield, contact interval between the neutral wires, ground shield dielectric properties, frequency, etc., to provide some insight into the range of conditions which might be encountered during field PD testing of unjacketed distribution cable as well as the contribution to power frequency loss.