Fig. I. Location of SC cables and main bus bars. current totals 2.5 MA. This value of the current presents no problem for a SC cable system, but the allowable bending radius does. Cables will be wound on drums to reduce the number of connections. But the size of the drum is limited for the transportability by the space shuttle, and must be as small as possible. In the next step, the maximum current of bus bars must be decided, which is one of the major factors determining the efficiency of the subsystem. In order to reduce the Joule losses, the electric power collected from solar cells ought to be transported to SC cable system immediately. In this case, a large number of terminations are necessary. On the other hand, too many terminations are not desirable, from the point of the view of decreasing the load of refrigerators. Compromising with both of the Joule losses and refrigerating load reduction, it is decided to use 10 kA. The proposed location of SC cables and main bus bars is shown schematically in Fig. 1. The solar cell array of 10 km x 5 km consists of 25 sections of 2 km x 1 km, and each section has one termination of a SC cable circuit. Ten main bus bars of 4 kV 10 kA are connected to the termination. Each circuit consists of three SC cables for redundancy. The rating current of the designed cables is 1.5 times larger than the value required for ordinary operation, so that full power can be carried by two cables in case of the contingency of a failure in one of three.
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