Design, Construction and Operation of a Neon Refrigeration System for a HTS Power Transmission Cable

Abstract

A prototype of a gas-cooled high-temperature superconducting (HTS) power transmission cable has been manufactured and tested at variable cryogenic temperature in the range 30-70K. For this temperature range a Ne refrigeration system based on the Joule-Thomson cycle has been selected. The Ne refrigerator consists of two Ne-Ne counterflow heat-exchangers and a Ne-LN2 heat exchanger as pre-cooler. The main Joule-Thomson throttle valve reduces the pressure of the precooled Ne from 200 bar to the operating pressure ofthe cable rated at 15bar. The throttle effect lowers the temperature to about 45K. Lower temperatures are possible at a lower rated operating pressure whereas higher temperatures can be obtained by activating a heater. In order to improve the refrigeration power and to match the cable pressure to the suction pressure of the Ne compressor a second valve was used on the low pressure side of the refrigerator. The design and construction of the cryogenic system is presented, focusing on the practical aspects of heat-exchanger manufacture, cooling of the current leads, gas management system and upgrade of a commercial high-pressure, oil-free compressor for work with Ne.