Microscopic Electric Field Enhancement on Contact Surface in Vacuum Interrupters with Contact Gap 10-60mm

It is widely known that microscopic electric field on contact surface in vacuum interrupters (VIs) is fundamental to study vacuum breakdown mechanism based on different breakdown initiating theories, such as micro-particles initiating mechanism, field emission initiating mechanism and so on. Furthermore, the microscopic electric field enhancement on the contact surface is influenced by contact gaps. The objective of this paper is to investigate the relationship between the microscopic electric field enhancement and the contact gap based on the modeling of the shape contours and the microscopic rough contours of the micro-protrusions on the contact surface in VIs. In this paper, the shape contours of the micro-protrusions are measured by Scanning Electron Microscope (SEM) and the rough contours of the micro-protrusions are extracted by Atomic Force Microscopy (AFM). In order to establish the microscopic rough contours based on the Weierstrass-Mandelbrot fractal model, wavelet analysis is used to extract the fractal dimension and the genetic algorithm is used to extract the fractal scaling constant. The shape contour which is fitted by polynomial functions is superimposed on the rough contour. Then, a complete micro-protrusion model is established. Finally, the electric field distribution of the micro-protrusion model on the contact surface with the contact gap of 10-60mm is simulated. The results show that the microscopic electric field enhancement depends on the 0.09 power of the contact gap for the 10-60mm contact gap. The results of this paper may provide some useful information to study the vacuum breakdown mechanism.