Development of an improved extruded dielectric cable rated 230 kV

Work performed on developing an improved 230 kV extruded solid dielectric cable, the techniques of jointing such cables and the testing of terminations suitable for operation at that voltage level are described. Difficulties were encountered during manufacture in applying the semi-conducting extruded conductor shield. A new higher melt point compound solved the problem. A joint capable of operating at the 230 kV level was developed but showed a deficiency under voltage impulse testing while the conductor was at elevated temperature. A reduction in contract scope terminated this effort. Two terminals rated for 230 kV were found to be commercially available from domestic manufacturers. The limited testing performed showed them to be compatible with the cable cross-linked polyethylene insulation and electrically sound under 60 Hertz testing. No direct voltage or impulse voltage testing was performed on the terminations. A sample circuit, consisting of cable and joint, was subjected to impulse voltages at both room temperature and normal conductor operating temperature of 90/sup 0/C. While the cable only was able to withstand voltage impulses in excess of the Basic Impulse Level (BIL) at room temperature, it failed at BIL while conductor was heated to 90/sup 0/C. In like manner, a cable and joint circuit was assembled. Similar voltages were impressed at room temperature without incident. The joint failed at 90/sup 0/C conductor temperature. Cable, joint and termination were assembled in a simulated circuit and subjected to conductor loading to elevate temperature while 60 Hz voltages in excess of normal operating levels were continuously applied