Design and Testing of a High-Voltage Temperature Transducer for ITER High-Temperature Superconducting Current Leads

The high temperature superconducting current lead (HTSCL) plays key roles in supplying large current into the ITER superconducting magnets. To measure the temperature of HTSCL, which is cooled by helium gas, PT-100 sensors are installed at both the warm end of the HTS section and the roomtemperature (RT) terminal. These sensors are exposed to highvoltage environment, depending on the type of ITER magnet. For instance, in the case of the Poloidal Field (PF) coils, the voltage along the HTSCL can reach up to 14 kV under normal operating conditions and up to 29 kV under fault conditions. Due to the high potential difference between the ITER magnets and ground, careful consideration must be given to the design of the temperature measurement interface and the analog signal conditioning from the sensors installed on the HTSCL. This paper presents the design, fabrication, and test results of the temperature measurement system specialized for HTSCL, referred to as the High-Voltage Temperature Transducer (HVTT). Based on the technical specifications provided by the ITER Organization (IO), functional test results, such as measurement accuracy and high-voltage test, are discussed. In addition, a long-term operation test conducted on the PF current leads of the KSTAR tokamak at the Korea Institute of Fusion Energy (KFE) is introduced.