Development of a 69kV High-Pressure Gas-Filled Pipe-Type Cable System for an Arctic Environment

A high-pressure gas-filled (HPGF) pipe-type cable system rated 69kV has been developed for operation at Prudhoe Bay, Alaska, which is at the North Slope above the Arctic Circle. A minimum ground ambient of -10°C is applicable to the major portion of the circuit which is buried. The cables installed in pipes across a 46 m (150 foot) long bridge, the terminal riser cables and the cable terminals experience a minimum air ambient of -48°C. The cable design for each of these ambient temperatures required special consideration with regard to the insulation structure and impregnant to be employed for the paper insulation. This paper describes the investigation of materials, cable models and prototype cables to achieve the physical and electrical properties required for the application. For the buried cable, a polybutene impregnant having a viscosity lower than normally employed for HPGF cable was used. For the cables exposed to the lower ambient air temperature, a phenylmethyl polysiloxane silicone fluid was selected as the impregnant. A transition joint between the polybutene and silicone impregnated cables was developed. Standard gas-filled terminals were modified for service at the low ambient air temperature. The successful completion of this R&D project has provided a rugged, reliable high voltage cable system suitable for transmitting power in an arctic environment.