Low-Frequency Operation of Switching Vacuum Arcs

Abstract

Conventional applications of vacuum interrupters cover a broad operating frequency range from 60 Hz down to 16.7 Hz, as typically found in power networks and railway electrical systems. With the increasing integration of alternative power sources and the growing complexity of decentralized power networks, new requirements are emerging for vacuum interrupters. Under these evolving grid conditions, fault events may occur at significantly lower frequencies than in traditional systems. Such low-frequency operation can lead to extended arcing times, higher transferred charge, and increased thermal stress on the interrupting contacts. To address these challenges, the present work investigates the arc behavior at frequencies between 2 and 4 Hz and current levels ranging from 70 to 2000 A, using a combination of optical diagnostics and electrical measurements. In addition to high-current experiments, several synthetic test series incorporating transient recovery voltages (TRVs) were conducted to evaluate interruption performance under realistic fault conditions. Furthermore, key aspects of current interruption, such as transferred charge, thermal loading, and contact erosion, were analyzed through numerical simulations and compared with established data obtained at conventional power frequencies. Both the experimental results and the simulation studies demonstrate that vacuum switching arcs exhibit excellent stability and interruption characteristics, confirming that vacuum remains a highly suitable medium for low-frequency current interruption in future power system applications.