The Effect of DC Electro-thermal Ageing on Electrical Treeing in Polyethylene

Abstract

Electrical treeing is among the main mechanisms responsible for electric breakdown in polymeric high voltage cables. In this paper, electrical treeing in electro-thermally aged low density polyethylene (LDPE) was evaluated by means of a real-time microscopic detection system. A wire -plane electrode test object with semiconducting tab was used in the study. The ageing was performed at a constant temperature of 80°C and an applied DC voltage of 10 kV of both polarities and lasted from 100 up to 800 hours. For testing the resistances to electrical treeing, tests were performed by applying 50 Hz AC voltage at a ramping speed of 0.5 kV/s. The obtained experimental results showed that mainly the thermal component of the ageing had an influence on electrical treeing parameters, namely on the initiation voltage as well as the shape and occurrence frequency of the trees. With an increase of the ageing time, the tree inception voltage gradually decreased.

Invariant electrical conductivity upon thermal ageing of a crosslinked copolymer blend for high voltage insulation

“…Ageing of polyethylene-based insulation materials can introduce chemical defects as well as structural changes, which can negatively affect their dielectric and thermo-mechanical properties 22–26 and hence may cause electrical treeing as well as a decrease in the dielectric breakdown strength. 27–30…”