Methods to Calculate the Current Leads of AC High-Temperature Superconductor Cables

Abstract

Practical use of power transmission cables based on high-temperature superconductors (HTSC cables) can be accounted for by their high throughput. Despite the large number of HTSC cables, experimental ones and those operating as parts of existing networks, the issues of using high-current liquid-nitrogen-cooled three-phase HTSC cables for the transmission of high-power electricity from power plants remain poorly studied. The injection of alternating current into the cable system imposes a number of specific limitations in the design of current leads. Most superconducting devices are dc devices, and so there are almost no techniques for calculating high-voltage high-current ac current leads. This paper discusses the particularities of operation of ac current cryoleads and proposes the principles of their calculation that allow one to increase the active power transmitted through them. The sequence of determining the geometrical dimensions of supporting insulators of current leads, which determine the total length of current leads, is shown as a function of the external environmental conditions. The effect of heat transfer in a nitrogen gas medium on the thermal mode of the current lead has been considered. It has been established that the effect of cooling on the thermal mode of the current lead is much less than that of the heat release and heat distribution due to the relatively small specific heat capacity of gaseous nitrogen. The parameters of self-cooled copper current leads designed for 12 kA are considered at cooling temperatures of 65 and 77.4 K as an example.