Insulation Resistance Measurements of Medium-Voltage Cross-Linked Polyethylene Cables under Thermal Stresses

The insulation of medium-voltage electrical cables is usually composed of polymers such as cross-linked polyethylene (XLPE) that excel in electrical dielectric properties and thermo-mechanical reliability. Thermal stress is one of the key factors that degrade the insulation performance of heavily loaded cables and eventually cause irreversible cable failures. To inform XLPE insulation resistance (IR) changes which measure cable insulation conditions under thermal stresses and assist in the development of related IR models, this paper presents IR measurements of 10 kV XLPE power cables which were thermally aged at around 100 øC under an accelerated thermal ageing experiment. The yearlong IR observations exhibited two consecutive U-shape changes followed by a rough decline, which might reflect a joint effect of annealing and thermal ageing. The experiment results highlight the necessity of enhancing IR models to additionally consider the promotion of hopping conduction within insulation by the chemical components diffused from semicon layers under the annealing effects.