Magnetic Investigation of the Arc Ignition Process in a Model Vacuum Switch during DC Interruption Tests

Inhalt:
Vacuum switches have been in use for decades and are state of the art in medium-voltage AC networks. Their properties and switching behaviour are largely known for the contact geometries used today. With an increasing share of DC loads and renewable energies, meshed DC grids are becoming more and more attractive. Such grids need reliable switches in order to be able to safely connect and disconnect loads and generators. Vacuum interrupters are an interesting candidate for such switching tasks due to their cost-efficiency, their reliability in AC voltage networks and their climate friendliness. It has not yet been conclusively clarified whether the contact geometries used in commercial vacuum interrupters for AC networks are also the best possible for interrupting DC. This work presents a possibility to analyse the arcing behaviour of contact geometries at the ignition time magnetically by using Hall sensors, that can be used on commercially available vacuum interrupters as well. Measurements are conducted with a model vacuum interrupter and axial magnetic field contacts. During these measurements up to three initial arcs have been observed at the moment of contact separation. The magnetic Hall system was able to detect singular arcs consistently. Footage of a high-speed camera confirmed the Hall system measurements. The phenomena of multiple arcs at the moment of contact separation needs further investigation.