Breakdown properties of aged low voltage cross-linked polyethylene insulated cable

Abstract

In this study, the electrical breakdown strength tests were performed on low voltage insulation material, crosslinked polyethylene (XLPE) insulated cable rated at 0.6/1 (1.2) kV. In Malaysia, this type of cable was found to have premature degradation within three to five years of service. The objective of this experiment is to study the characteristic of XLPE used as the insulation material of the aged cable. The allowable maximum operating temperature of this cable is at 90 °C. New cables of different manufacturers were tested and a degraded cable taken from field was used as a reference sample. The thermal consequences on each cable were compared. XLPE sheets sliced from the cable insulations were prepared as the test samples. New samples were heated to a temperature of 90 °C to accelerate the ageing process in an oven. An electrical breakdown tests were carried out to assist the evaluation of the degradation on the unaged and aged cables. It has been shown by the experiment that the electrical properties of the aged XLPE of low voltage cable for both manufacturers were greatly affected when exposed to the heat. This can be considered as defect to the manufacturing process because the insulation layers could possibly be made of a substandard material, that fails to perform according to the specification.