Simulation of switching arcs in climate-neutral 420 kV earthing switches and disconnectors filled with Clean Air

The investigation of various SF6-alternatives is even more in the focus of current research and development efforts. In this context, gas-insulated switchgear with Clean Air (80% N2 and 20% O2) insulation and the use of vacuum switching technology for the circuit breaker can represent an environment-friendly (GWP = 0) and highly performant SF6-free solution for future high-voltage switchgear applications. Within this framework, this contribution focusses on the modelling and simulation of switching arcs in the active back parts of a Clean Air-filled gas-insulated switchgear, namely the earthing switch and disconnector. The presented arc model uses an alternative 2D axisymmetric simulation approach where the arc attachment size is conserved by means of a scaling of the arc current. In contrast to the conventional 2D axisymmetric approach based on the assumption of the conservation of electrical current, the presented alternative approach allows the electrical arc simulation away from the geometrical symmetry axis. The simulation results are in good agreement to the measurements in a real earthing switch configuration validating the new simulation approach.