Fast computation of breakdown voltage in air outside vacuum interrupters

A tool capable of computing the breakdown voltage of industrial devices in a fast and direct way is highly desirable. This work employs a stationary self-consistent method, the so-called resonance method, for computing the inception voltage of a low-current discharge, which in many cases of industrial relevance is virtually the same as the breakdown voltage. The tool was employed in a previous work for a simple configuration with a dielectric cylinder placed between two electrodes, and the inception and breakdown voltages coincided with an accuracy of 5%. In this work the tool is applied to conditions of specifically designed experiment for investigation of breakdown in the exterior of vacuum interrupters (VIs); a topic of enhanced industrial interest due to the use of VIs in high-voltage circuit breakers in connection to environmental policies determining the reduction in the use of SF₆ in new industrial applications. The modelling results are in good agreement with experimental data for various air pressures. The tool is efficient in a vast range of conditions and provides the inception voltage of a specific setup as an output, thus avoiding a lengthy trial-and-error procedure of determination of the breakdown voltage involving time-dependent simulations.