Effect of the contact diameter on the vacuum arc plasma parameter in high current vacuum arcs

The reduction of sulfur hexafluoride utilization constitutes a pressing global challenge in the development of eco-sustainable power apparatuses. Developing vacuum circuit breakers for transmission-level applications represents a strategic solution to this challenge. This development requires upscaling contact diameters, making it imperative to understand arc behavior under these expanded contact conditions. However, systematically obtaining arc parameters through experimental approaches currently poses significant challenges. The objective of this study is to numerically obtain the vacuum arc plasma parameters under five large contact diameters of 80, 100, 120, 140, and 160 mm. A two temperature magnetohydrodynamic model was built to simulate vacuum arcs. The results show that as the contact diameter increases, the temperature, number density, and pressure exhibit progressive reductions. The current density exhibits a sharp decline with increasing contact diameter. Under larger contact diameters, the axial magnetic field demonstrates enhanced effectiveness in suppressing current constriction compared to smaller diameters. Using anode input heat flux density as the critical criterion, interruption risks were evaluated for each contact size. For a typical discharge condition for a high voltage level vacuum switch with 40 kArms short-circuit current, 3.6 m/s opening velocity, and 200 mT axial magnetic field, the recommended contact diameter range of 120–140 mm balances interruption reliability and practical application requirements.