Design and first stage test of 50-meter flexible superconducting cable

A 50-meter flexible superconducting cable model is described, including a copper-stabilized Nb
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Sn-tape current-carrying core and cable-paper electric insulation of 13 mm total thickness which is submerged in cold helium while under working conditions. The helium-cooled inner channel is 36 mm in diameter and the outer diameter of the current-carrying core is 75 mm. Helium also flows in an annular channel between the outer surface of the core and a corrugated enclosure. The core is incorporated in a flexible cryostating envelope consisting of 4 corrugated enclosures; the two middle pipes form an annular channel for liquid nitrogen which reduces heat leaks to helium. The design of a 110 kV, 12 kA lead was developed to test the flexible superconducting cable model. For d.c. and a.c. tests of the model, a technique of inductive current introduction through a superconducting transformer is offered. A multisection transformer with a superconducting primary of insulated Nb
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Sn tape was manufactured, the current-carrying core being the secondary. Before assemblying, the sections were tested in a liquid helium cryostat to check the design characteristics and to determine the critical current in the winding. A.C. losses (50 Hz) in the transformer's primary were measured. The cable model was cooled by two improved helium refrigerator plants, HGU-150/4,5. Current tests were performed at a working temperature.