Arc extinction with nitrogen at 1-40 bar in a puffer-like contact configuration

To develop cost-efficient subsea switchgear for large sea depths, the extinction of arcs under high filling pressures must be understood. In this work, arc-extinction experiments have been performed with a puffer-like contact configuration using nitrogen at different filling pressures as the current interruption medium. The main finding is that, for the given contact configuration, the current interruption capability was lower at 20 and 40 barabs than at 1 and 10 barabs. While higher pressures result in higher cooling flow rates and longer flow times given the same puffer volume, compression spring and nozzle geometry; it does not necessarily improve the arc-extinction capability. This is probably because higher filling pressures increase the arc voltage and total energy dissipated in the arcing zone. Because the filling pressure greatly influences the flow characteristics, the puffer design should be optimized for each pressure level. Keywords: Current interruption, subsea switchgear, medium voltage, high-pressure nitrogen