Vacuum switching, a well proven technology has found its way into resistance-type load tap changers

For 30 years vacuum interrupters have been successfully integrated into reactance-type load tap changers (LTCs). This proven technology is now finally becoming available for resistance-type LTCs. This document explains the technological developments that enabled the introduction of vacuum interrupters into resistance-type LTCs and describes the switching principles of reactance- and the newest resistance-type LTCs that utilize vacuum interrupters. Additionally the advantages of the vacuum technology with respect to reliability, contact life, mechanical life, inspection cycles and economy are discussed.