Optimisation of the switching process by modelling the contact surface

The aim of this paper is to show the design procedure of a disconnector starting at basic modelling up to a product used in practice. The relation between switchgear mechanics and electrophysics arc phenomena is discussed and the influence of short arcs on the opening contacts of a high voltage disconnector is analysed. With regard to contact erosion the most severe switching stress occurs during the bus-transfer current switching procedure. Based on simplified models the influence of various parameters on the contact design and the disconnectors reliability is discussed. Finally a new contact design using main and auxiliary contact fingers is shown. The system uses the spring effect of flexible fingers mounted on the main contacts. The new disconnector type fulfils the type tests according to the appropriate international standards and is successfully used in practice.