Quality Assurance of Vacuum Interrupters Intended for Transmission Voltage Level Application

Vacuum Interrupters (VI’s) have since their first commercial introduction in the late 1950s proven to be an extremely reliable component for use in Low- and Medium-Voltage power switching applications. Today Circuit-Breakers based on vacuum technology dominate the distribution voltage level markets.Recent developments, where single-break VI’s have been introduced into the lower transmission voltage level starting from 72.5kV and being applied in (high pressure) gasses other than air, raised the question if the current customary quality assurance measures are one-to-one applicable to these novel types of interrupters. Till now, due to strict quality control and proven design, manufacturing and measurement techniques all VI’s leaving the factory are "sealed-for-life".The current proven practice of leak-rate detection for VI’s as also some basic design considerations like the use, selection and placement of getter materials are being discussed. Today’s common measurement technique will be looked at in more detail to see if it is also applicable to High-Voltage VI’s, which generally are substantial larger and being applied in other gases than air, like e.g.: N2, SF6, CO2, Novec^TM or other gas mixtures under high pressure up to about 0.8MPa.Finally, results and recommendations are being discussed.