Simulation of the electric field in vacuum main switches

The company Richard AG develops and manufactures circuit breakers, contactors, insulators and fittings for worldwide use in traction power supply. It also provides service and technical support for the railroad industry and transport. Meeting individual customer requirements with maximum flexibility is one of Richard AG's main objectives. To ensure robust operation of vacuum main switches, the prevention of damage due to corona discharges and breakdown voltage is crucial. A numerical simulation was performed with Ansys Workbench for new requirements that are outside the previous standard. The aim was to validate the design for the changed operating conditions.

The calculations carried out by CADFEM using Ansys simulation tools have given Richard AG the following advantages:

• The new operating conditions could be validated.
• A more detailed knowledge about the design of the vacuum main switch was gained, especially in the identification of the critical points.
• Special information was obtained that was not previously provided by experimental measurements.

An electrostatic simulation with adjusted maximum voltages was used. The calculation of the voltages and electric field in the various components of the circuit breaker made it possible to gain accurate knowledge of the field distribution. Since even minute geometric details present potential hazards, accurate consideration of the detailed geometry allowed the most critical points of the design to be identified. To qualify the design comprehensively, it has been taken into account that different structural components and gases have different electric breakdown limits. Therefore, multiple electric field boundaries have also been considered. Numerical simulation has been performed to ensure field distribution and compliance with critical limits for both standard and new operating voltages.