4/16/2023 0 Comments Gravit designer splice tool![]() ![]() ![]() 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. 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. No direct voltage or impulse voltage testing was performed on the terminations. The limited testing performed showed them to be compatible with the cable cross-linked polyethylene insulation and electrically sound under 60 Hertz testing. Two terminals rated for 230 kV were found to be commercially available more » from domestic manufacturers. ![]() A reduction in contract scope terminated this effort. 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 new higher melt point compound solved the problem. Difficulties were encountered during manufacture in applying the semi-conducting extruded conductor shield. 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. All twelve samples survived the program intact, demonstrating their qualification for utility service. Despite a variety of problems with the terminations and interconnecting cables, which caused modifications to the test conditions in the final stages, the test program was completed successfully. In a switching surge test after load cycling and with the conductors at 90/sup 0/C, one of the splices failed at 700 kV, more » which compares well with the rated switching surge withstand requirement of 550 kV. The two splices with the conductors at 90/sup 0/C withstood 5 positive and 5 negative 1.5 x 50 microsecond impulses at 650 kV, both before and after load cycling. These losses were essentially constant over a temperature range of 23/sup 0/C to 130/sup 0/C. Capacitance and power factor were in the order of 195 picofarads and 0.25% respectively. The corona extinction level of 120 kV (5 pc) and dielectric losses of the splice were unaffected by cyclic loading up to 130/sup 0/C when stressed at 1.5 times normal line to ground voltage. The splice, using the hand tools and installation instructions disclosed, can be assembled (including cable preparation) by two men in about five hours. The splice makes use of premolded, interference-fit, elastomeric components that can be factory tested (to guarantee their integrity) before they are installed, thereby increasing the reliability of the system. It has passed all the design requirements and is ready for a prolonged trial simulating an actual installation. A straight splice for 138 kV extruded dielectric cable has been developed under this contract. ![]()
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