Three-Conductor Compressed Gas Cable Optimization. Final Report

摘要

The research and development program is described for a three-conductor compressed gas-insulated transmission line (CGIT). This includes the design and optimization of the sheath, conductors, posts and conical support insulators, and compressed gas insulation system. Calculations were made of the transient short circuit forces on the conductors and insulators. Two prototypes were made of a new design of 362 kV three-conductor system of buried rating 2000 A. The system was constructed by extruding the aluminum sheath in three segments, supporting the conductors on post insulators in each segment, and then welding the three segments together to form the completed CGIT section. The short circuit prototye passed 63 kA short circuit tests (0-G, 0-0, 20-G, 30) and there was good agreement between the measured and calculated forces. The high voltage prototype and trifurcation passed the high voltage design tests of 500 kV rms, 1050 kV BIL and 825 kV switching impulse. Tests were made of the system at full rated current (2000 A), and the temperature distribution on the conductor and sheath agreed with a new thermal analysis that was developed. A detailed cost breakdown and economic analysis is given of the three-conductor and isolated phase CGIT systems for voltage rating 145 kV through 800 kV, including the cost of installation and operation. The analysis indicates that the three-conductor CGIT systems have a lower effective installed cost (9 to 14%) than the isolated phase systems for buried installation, have lower losses of 12 to 36%, required a narrower trench and need only one third the number of field joints, resulting in a simpler, faster field installation. (ERA citation 04:046368)