Upgraded KSTAR Toroidal Field Coil Quench Protection System

Abstract

The upgradation of the Korea superconducting tokamak advanced research (KSTAR) toroidal field (TF) superconducting coil quench protection (QP) system has been performed since the failure of the 40-kA dc interruption switch of it in 2016. The complicated design and protection logic led to the accident of the QP switch during the malfunction of the interlock power-line carrier (PLC). To improve the reliability of the TF coil QP system, the KSTAR decided to apply the pyrobreaker (PB) from the Efremov Institute as a backup for the slow discharge (SD) and QP switches. In addition, the upgraded design segregates the QP circuit from the SD circuit. The simulation was performed to analyze the TF coil QP system with the consideration of the switching behavior of the PB and the stray parameters of the circuit. The upgraded KSTAR TF coil QP system has been designed, manufactured, installed, and tested successfully. This article will present the issues of the previous design of the KSTAR TF coil QP system and the results of the upgraded system.