Dielectric considerations for a superconducting cable termination

A high temperature superconducting ac cable transmission system where the losses are vastly reduced compared to traditional methods appears to be an attractive option for electric supply companies. An increase in power transfer for the same or lower voltage would result through the use of such a system. However, there remain a number of important technical issues to be addressed before companies are willing to accept this technology. One component of the power system which has an important role to play in the secure transmission of power from cryogenic to ambient temperatures is the termination. This must operate through axial and lateral temperature differences exceeding 200 K with good thermal efficiency and in the presence of high voltage such that the electric stress through the termination is controlled. The work described in this paper forms part of a project investigating several key design aspects of a high temperature superconducting termination. These include the electrical insulation and stress control through the transition from liquid nitrogen temperatures to ambient and the parameters affecting the central thermal element in the termination, the current lead.