RESEARCH UNIT: ISTP-Padova
WP LEADER: NICOLÒ MARCONATO
The knowledge of the physical mechanism governing the vacuum breakdown still remains an open issue although
decades of research activities were dedicated to study this topic. This WP proposes the creation of an advanced laboratory for the study of electrical insulation related issues in fusion machines. The main topics are high and extra-high voltage insulation in vacuum and pressurized gases, composed of two activities: the refurbishment and upgrade of the facilities of the High Voltage Padova Test Facility (HVPTF) for the study of vacuum insulation in high and very high voltage systems and the setup of a new feature of the HVPTF for the study of pressurized gas electrical insulation properties in high and very high voltage systems.
The most relevant outcome of this WP will be:
The HVPTF has been used to tests stainless steel electrodes insulated by high and medium vacuum, and the experimental results have been used to benchmark a probabilistic code able to predict the maximum hold off voltage of a generic system insulated by vacuum with a generic electrode geometry.
The design and the installation of a new system composed by an improved vacuum vessel, upgraded cables and
feedthroughs will face one of the main issues observed after several years of operations in the HVPTF , which is the reliability of the system against the energetic vacuum arcs (>500kV), usually occurring during the experimental campaigns.
Moreover, in many applications from the industry to fusion technology, where high power must be transmitted in high voltage DC lines with a high level of compactness and reliability, the choice of Gas Insulated Lines (GIL) would have several advantages to feed high power system in fusion facilities (higher transmission capacities, low losses, and greater overload capabilities than other cable technologies).
Whether the GIL technology in AC is mature and widely adopted in commercial application, HVDC GIL technology must face various issues still unsolved, like charge carrier accumulations on dielectric interfaces, which may lead to a decrease in flashover voltage, requiring the understanding of the physical processes and factors of influence on the electric field distribution. The design, procurement and installation of a new system composed by a real size pressure vessel with proper air-gas bushing, HV power supplies rated to 500 kV, suitable diagnostics for gas monitoring and measurement of electric properties, and with appropriate acquisition and control system will face this relevant issue.