Influence of no-load operation and current switching on breakdown characteristics of high voltage vacuum interrupters at contact gap 30mm

It is important to understand dielectric strength of vacuum interrupters after no-load operation and current switching, which reflects a dielectric condition of the vacuum interrupters operating in field. Especially there is no such data available for high voltage vacuum interrupters with contact gaps reaching 30mm. The objective of this paper is to experimentally investigate the influence of three kinds of switching operations on the standard lightning impulse voltage breakdown characteristics of high voltage vacuum interrupters with a contact gap 30mm. The three kinds of switching operations are “closing without current / breaking without current”, “closing without current / breaking with 5kA current” and “closing without current / breaking dc current”. Therefore we designed six high-voltage vacuum interrupters with butt type contacts. The experimental results revealed that the conditioning process became slowly and the breakdown voltage followed the Weibull distribution after the three kinds of operations. And the operation “closing without current / breaking 5kA current” will increase the 50% breakdown voltage U₅₀ of the vacuum interrupter from 340kV to 394kV. The U₅₀ of the vacuum interrupter after the operation “closing without current / breaking without current” will increase from 340kV to 362kV. The operation “closing without current / breaking dc current” will increase the dielectric strength. As the current is increasing. The U₅₀ increased from 385kV to 395kV with the breaking current 450A dc 500ms. And the U₅₀ increased from 385kV to 437kV with the breaking current 750A dc 500ms.