VERIFICATION OF LV UNDERGROUND CABLE INSULATION BY AIR INJECTION

This paper presents the development of a new method for verifying the mechanical integrity of the insulation of lowvoltage cables in order to ensure a quality installation and prevent potential arcing faults. The approach consists in injecting compressed air into the cable core and to observe the subsequent pressure variations. The diagnosis of insulation failure (leak) is based on the reduction rate of the pressure of the air stored in the cable once the injection has been stopped. Conclusive results were demonstrated during a comprehensive laboratory validation program as well as on the distribution network. Prototypes developed based on this method were successfully tested on Hydro-Quebec’s underground distribution network.