The relationship research between the permittivity and internal pressure in vacuum interrupters

The Vacuum Circuit Breakers (VCBs) are typical types in the medium voltage distribution switches, and the internal pressure (P) in the vacuum interrupters affects the working quality and life. With the development of national smart power grids and the maintenance system based on reliability, on-line monitoring of the internal pressure in the vacuum interrupters becomes necessary and urgent. With the increasing of voltage level in VCBs, requirements of, internal pressure on-line diagnosis devices were highly recommended by Smart Grid, especially for the 35kV, 72.5kV and above voltage level. At present, the popular domestic on-line monitoring methods are achieved by detecting the potential of vacuum interrupter shield (Uc), the solving analysis of Uc makes significance meaning to the on-line monitor theory of the internal pressure. The relationship of the internal pressure(P) and s_r was studied, the expression of P and 8r was concluded on dry air condition, and emulation mode conditions was provided for studying the relationships of internal pressure(P) and potential of vacuum interrupter shield(Uc). Necessary theoretical and technical support was supplied for the intelligence and condition-based maintenance for VCBs, and this work is valuable for reference engineering application.