29th Symposium on Fusion Technology (SOFT 2016)

P2.081 Design and Testing of Crowbar Protection System for the JT-60SA Superconducting Magnet Power Supplies

6 Sep 2016, 14:20

1h 40m

Foyer 2A (2nd floor), 3A (3rd floor) (Prague Congress Centre)

Board: 81

Poster E. Magnets and Power Supplies P2 Poster session

Speaker

Zito Pietro (FSN-FUSTEC-IEE)

Description

JT-60SA is a Superconducting Tokamak in the framework of the Broader Approach Agreement between Europe and Japan. For this International Project, both the Italian National Agency for New Technology, Energy and Sustainable Economic Development (ENEA) and Comissariat à l’Energie Atomique et aux Energies alternatives (CEA) are providing ten AC/DC converters for the poloidal superconducting magnets (rated in the range ±20kA, ±1kV), two converters for fast plasma position control coils (rated ±5kA, ±1kV) and a converter for the toroidal superconducting magnets (rated +25.7kA, ±80V). Each converter is equipped with a crowbar protection system. These equipments are under construction and testing by Jema and Poseico industrial suppliers. The crowbar system has to carry the current flowing through superconducting coils, during faults or plasma disruptions, to protect the AC/DC converter and the superconducting coil from over-voltages even in case of earthquake events, it is considered as a safety relevant component and it is designed to be seismic resistant. The circuit configuration is based on a hybrid-making-switch, composed by a bidirectional-static-switch with a mechanical-switch and a varistor in parallel. The static-switch is composed by eight thyristors in bidirectional configuration (four connected in parallel and four in antiparallel), and it is designed to be able to safely intervene even if one thyristor or the mechanical-switch is not operating. The mechanical-switch (rated 50kA making-capacity) takes some tens of milliseconds to close, limiting the conduction time of thyristors. The overvoltage protection is performed by a voltage transducer, a Break-Over-Diode and a varistor assuring a fast intervention with a high redundancy protection level. The current capability test of crowbar system required a maximum peak current of ±26kA and a maximum specific energy I²2t = 4.6GA²2s for TF SCMPS. Finally the crowbar system and DC bus-bars were subjected to seismic tests in laboratory.