My Journey into Emptiness: HF Phenomena in Vacuum Arcs and their Impact on Current Interruption

This paper is giving an overview of personal experience in research, development and testing of many types of vacuum switching devices. The common denominator is high-frequency (HF) phenomena.The overview starts with vacuum arc instability and current chopping and goes on into HF current interruption, first related to small-current interruption in research-type and commercial low-surge interrupters, later to high-voltage DC vacuum circuit breakers using very large HF currents. The fast phenomena occurring upon ‘late’ breakdown are discussed including analysis of field-electron emission (FEE) current. A conclusion is that FEE is not directly related to late breakdown in a full-power set-up.High-current interruption is discussed showing evidence of very large post-arc current in practical fault interruption. Modelling attempts of high-current interruption shows the complexity of the processes. An example of a hybrid vacuum/SF6 circuit breaker is discussed.In the second part of the paper, the author’s observations and expectations on high-voltage vacuum circuit breakers, novel actuators and insulation issues are shared. Trends and future directions of vacuum switching technology are reviewed, including research gaps and opportunities.