Properties of switching vacuum arcs in high-voltage applications

• Applicants: Professor Dr.-Ing. Michael Kurrat; Professor Dr. Dirk Uhrlandt
• Subject Area: Electrical Energy Systems, Power Management, Power Electronics, Electrical Machines and Drives ; Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 576950665

Circuit breakers for high currents at high voltages in power distribution networks traditionally contain materials that are harmful to health and the environment (the greenhouse gas sulphur hexafluoride SF6 and fluorine-containing nozzle materials such as polytetrafluoroethylene PTFE), which are crucial to their functionality. Intensive research is being conducted into alternatives. One of these is vacuum switches, which do not require any materials of concern, but have so far only been used in the medium-voltage range. In order to implement high-voltage circuit breakers with vacuum arcs, large contact gaps and series connections of contacts must be realized. However, the complex behaviour of arcs in vacuum switches with large contact gaps has not been sufficiently investigated. The electrode attachment modes of the arc, particularly at the anode, are decisive, as they lead to different electrode erosion. Deviations from symmetry play a major role in voltage resistance, particularly when two vacuum switches are connected in series. In addition, due to mechanical advantages, the respective movable electrodes in both switches are operated with different polarities. In preliminary investigations, significant differences in vacuum arc behaviour and anode attachment modes were observed when the anode is moved in one interrupter and the cathode in the other, which is a mechanically advantageous option. The reasons for this are not yet known, which makes the search for technical solutions difficult. In this project, the applicants want to investigate the special behaviour of long vacuum arcs depending on the polarity of the moving electrode. A suitable experimental setup of an optically accessible double contact system is available at the TU Braunschweig. The experience of the Leibniz Institute in Greifswald will be used to apply spectroscopic analyses in such a system for the first time. The aim is to elucidate the physical mechanisms involved in the formation of anode spots in long arcs and compare them with the known behaviour in short arcs. Imaging optical emission spectroscopy in the form of fast video spectroscopy will be used to determine the densities and temperatures of the atomic and ionic species in the vacuum arc. The challenge here is to take into account the expected deviations from Local Thermodynamic Equilibrium (LTE) and to dispense with common approximations. This will be achieved by using suitable model approaches for species densities and radiation transport. In addition, profiles of the surface temperature of the electrodes will be measured to assess the temporal and spatial erosion behaviour.

• DFG Programme: Research Grants