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