The Impact of Various Contact Structures on the Microscopic Surface Condition of Vacuum Interrupters During Capacitive Switching

The double‐break vacuum circuit breakers (VCBs) that utilize series break technology effectively increase the switching capability for capacitive currents, elevate the withstand voltage level, and reduce the likelihood of restrike, all without compromising the breaking capacity for short‐circuit currents. However, previous research studies have predominantly focussed on analysing the insulation properties of double‐break VCBs and improving their breaking performance, voltage distribution, and breakdown characteristics. The objective of this paper is to investigate the microscopic condition of contact surfaces in series‐connected vacuum interrupters (VIs) before and after 80 capacitive switching cycles using the AC fixed‐gap measurement method, specifically focussing on combination‐type designs where distinct contact structures are observed between the high‐voltage and low‐voltage sides. The findings suggest that the utilisation of a spiral‐type transverse magnetic field (TMF) in contacts significantly mitigates contact surface erosion compared to the use of a cup‐type axial magnetic field (AMF), both in individual and series‐connected VIs. These findings offer valuable insights into the design and optimisation of VIs for capacitive switching applications.