Quench Detection System for TF Coil-Test Campaigns of SST-1

Abstract

Testing of all superconducting toroidal field (TF) coils of a steady-state superconducting tokamak (SST-1) in nominal currents of 10 000 A under supercritical helium-cooled conditions was an essential prerequisite of SST-1 machine reassembly and subsequent refurbishment. Testing of individual TF coils at its full operational load of >;1 MA in its winding pack necessarily demands to test these coils with all the interlocks coupled with precise protection elements. A quench detection (QD) system is an essential and integral part of this testing since any irreversible off-normal scenario leading to the magnet quench must be promptly detected, and the energy from the magnet must be extracted with equal promptness to protect the magnet within the defined dump time, avoiding thermal stresses in the winding pack. An active fail-proof electronics QD system has been developed for the detection of resistive transitions in any part of the SST-1 TF coil. The difference configuration method has been adopted and exploited in the QD system for comparing the voltage drop measured in each of the double pancakes and interpancake joints of the TF coil. This paper describes the scheme of the QD system and precautions taken ensuring enhanced reliability and redundancy, as well as the results obtained in the due course of all the 16 SST-1 TF magnet tests.