Magneto-Optical Arc Analysis in Vacuum Switches

Project-Management

  Name Working area(s) Contact
Christian Dorsch M.Sc.
Magneto-Optical Arc Analysis in Vacuum Switches
+49 6151 16-20438
S3|21 406

Background

The medium and high voltage grid of the future will be faced with new challenges by the energy transition. Increment of the required switching capacity, automation, flexibility and the associated high switching frequency require an increased use of circuit breakers. Vacuum circuit-breakers already represent the state of the art in the medium-voltage level (U < 72.5 kV) and, by means of continuous further development, are also in the area of the high-voltage level. They are a climate-friendly alternative to SF6 circuit breakers. The objectives of the development of vacuum circuit breakers are therefore an increased switching capacity, while improving the service life.

The service life of the vacuum circuit breaker is largely determined by the stress on the metal contacts by the arc. The arc occurs by opening the contacts and interrupting the current (in case of error up to 30.000 A). The extremely hot arc leads to local melting of the contact material, which greatly reduces the switching capacity. To prevent this, special contact geometries are used, which set the arc in motion and distribute the heat energy evenly over a larger area.

Measuring principles

Two principles can be used to investigate the arc in a vacuum. With high-speed cameras, movement and intensity can be recorded in a model vacuum chamber with viewing glasses. Alternatively, a measurement technique developed in the department may be used which measures the magnetic field of the arc with Hall sensors. Several sensors are placed around the switching chamber. The measured magnetic field determines the position and shape of the arc. If the arc now moves between the contacts, this can also be measured. In addition, the current and the arc voltage are measured.

Left: Vacuum switch model with viewing tubes for optical measurement. Right: Commercial vacuum interrupter with Hall sensors for magnetic measurement
Left: Vacuum switch model with viewing tubes for optical measurement. Right: Commercial vacuum interrupter with Hall sensors for magnetic measurement

Goals of the project

As part of the project, a model switch is to be developed, which simultaneously allows optical and magnetic investigations. This should first confirm the magnetic measurement method. Subsequently, basic experiments can contribute to a better understanding of the arc behavior. This understanding then serves the further development of commercial vacuum circuit breakers.

The project is a cooperation between the Department of High Voltage Engineering of the TU Darmstadt (HST) and the Institute for High Voltage Technology and Electrical Energy Systems of the TU Braunschweig (elenia) and is funded by the German Research Foundation (DFG).