Influence of Current Interruption Operations on Internal Pressure in Vacuum Interrupters

Due to the impact of arcing on high-purity surfaces and bound residual gases, current interruption operations may influence the internal pressure in vacuum interrupters (VIs). In this paper, we investigate the temporal development of internal pressure in VIs immediately after a current interruption operation, both intrusively using a vacuum gauge and nonintrusively using the magnetron method. By means of an experimental test setup that consists of a vacuum test system to vary the internal pressure in punctured, nonvented VIs with active getter elements, we performed experimental test series under variation of internal pressure and arcing time. The experimental results indicate that arcing during the interruption operation predominantly causes a significant decrease in the internal pressure of up to several orders of magnitude, depending on the arcing time and the initial pressure before the current interruption operation. Based on a test series with passivated getter elements, we found that active getter elements have only a minor influence on the observed pressure decrease. With regard to a condition assessment of vacuum circuit breakers, we discuss the impact of the observed pressure reduction effect on the possibility of predicting the remaining service life of installed VIs.