Optimized post-type spacers for 3-phase SF6 insulated cables

If power cables insulated with compressed SF6 gas are to have widespread application, their installed cost must be substantially reduced from the present level. The 3-phase, as opposed to the single-phase, configuration has been viewed as a means for reducing cable cost since it allows the use of materials for the outer pipe which are less onerous to purchase and install.1,2 Another item affecting the cost of such a cable is the solid dielectric spacer required at frequent intervals to support the conductors. Post-type spacers, which are inherently less voluminous and easier to manufacture than the disc-type or cone-type spacer configurations commonly used in isolated-phase bus construction, offer the possibility of realizing appreciable economies, provided they are optimally designed. This paper reports on the development of a design method intended to minimize the volume of post-type spacers for 3-phase SF6 gas-insulated cables.