Assessment and study of existing concepts and methods of cryogenic refrigeration for superconducting transmission cables

A review of current programs to develop superconducting power transmission shows that current plans require helium refrigerators operating at 5 to 13 K and 3 to 15 atm pressure with compressor power input in the range of 1,300 to 3,500 HP. Large helium refrigerators and standard nitrogen plants were studied. An average outage frequency of about 18 per year is found to be typical for both. Cost and reliability studies of alternate refrigeration systems based on studies of components show that the best current system having a failure rate of once in 20 years consists of two full size oil flooded screw compressors in parallel, manifolded to two full size cold boxes and a liquid helium back up dewar. Costs are projected as being only slightly greater than preliminary estimates.