Articolo in rivista, 2022, ENG, 10.1016/j.fusengdes.2022.113356

Studies on high voltage dc cable connection to supply the acceleration grids of the Neutral Beam Injector for DTT

Santoro F.; Ferro A.; Murari A.; Granucci G.; Romano R.

Consorzio RFX (CNR, ENEA, INFN, Università di Padova, Acciaierie Venete SpA), Padova, Italy; CRF - University of Padova, Italy; CNR ISTP - Consiglio Nazionale delle Ricerche, Istituto per la Scienza e Tecnologia dei Plasmi, Sedi di Padova e Milano, Italy; DTT S.c. a r.l., Frascati (RM), Italy. e ENEA, Department of Fusion and Nuclear Safety Technology, Via E. Fermi 45, 00044, Frascati (RM), Italy

The Divertor Tokamak Test facility (DTT) is the new tokamak under construction in Frascati (Italy), with the main aim of testing different divertor magnetic configurations and technologies in view of DEMO. The Heating and Current Drive function will be provided also by one Neutral Beam Injector (NBI), accelerating negative Deuterium ions with an energy of 510 keV, giving an output power of 10 MW maximum. The Acceleration Grid Power Supply (AGPS), with 3 stages rated 167 kV each, will feed the NBI accelerator. For optical reasons, the insulating gap among the acceleration grids is at the limit of the voltage holding in vacuum, therefore frequent arc breakdowns (BD) among the grids will occur, requiring the quick switch-off of the AGPS to limit the arc energy. For the AGPS, beside the ITER-like scheme including gas-insulated HV components, an innovative approach based on the Modular Multilevel Converter (MMC) technology is being considered. This would include air-insulated HV converters, requiring a huge building volume, which at present is not available in close proximity to the tokamak building. The alternative of installing the MMC converters in a new building to be erected in an available area located far from the tokamak, and connecting the AGPS to the load with HV coaxial cables, is under study. This paper presents the studies carried out to verify the impact of the cables length on the arc energy, in case of breakdown among the grids, and to estimate the magnitude of the voltage oscillations due to resonance effects. These oscillations can occur not only between each hot pole and the return conductor, endangering the cable insulation, but also between the return conductor and local ground, with potential consequences on the laying method, the human safety and the electromagnetic compatibility with sensitive apparatus nearby, which have all been evaluated.

Fusion engineering and design (Print) 187 , pp. 113356-1–113356-6

Keywords

Neutral Beam Injector, Acceleration Grid Power Supply, Modular Multilevel Converter, DTT

CNR authors

Murari Andrea, Granucci Gustavo

CNR institutes

ISTP – Istituto per la Scienza e Tecnologia dei Plasmi

ID: 474848

Year: 2022

Type: Articolo in rivista

Creation: 2022-12-12 08:59:35.000

Last update: 2023-07-03 09:38:35.000

External IDs

CNR OAI-PMH: oai:it.cnr:prodotti:474848

DOI: 10.1016/j.fusengdes.2022.113356

Scopus: 2-s2.0-85145561853

ISI Web of Science (WOS): 000991401300005