Vacuum Current Interruption for Low Frequency Applications

(2...4 Hz). This synopsis presents a study that examines the operational boundaries and thermal performance of VIs subjected to such low-frequency fault stresses.

The objective of the work is to assess whether existing vacuum circuit breaker (VCB) technology can be reliably utilized in low- and very-low-frequency environments, with particular emphasis on arcing behavior, thermal loading, and contact erosion. The study integrates laboratory experiments with high-speed arc diagnostics and complementary numerical simulations.

Experiments were performed using a synthetic test circuit capable of reproducing fault currents of 1000-2000 A (rms) at frequencies between 2 and 4 Hz. Two contact designs, Transverse

Magnetic Field (TMF) and Axial Magnetic Field (AMF), were evaluated to characterize arc dynamics, erosion patterns, and interruption capability. High-speed optical measurements captured arc evolution over durations up to 200 ms, highlighting predominantly diffuse arc behavior under low-frequency excitation.

Simulation analyses compared interruption characteristics at 50/60 Hz with those at 16.7, 4, and 2 Hz. The results indicate substantially longer arcing times at low frequencies, accompanied by lower arc energy density, reduced thermal stress, and minimal contact wear. Despite the extended arc duration, dielectric recovery remained manageable, and thermal limits were not exceeded. Arc imaging further confirmed that both TMF and AMF contacts sustained stable, low-energy diffuse arcs across all tested conditions.

Overall, the findings demonstrate that conventional VCB technology maintains robust performance under emerging power system conditions characterized by low-frequency faults, confirming its suitability for future converter-dominated network architectures.