Colloquia

Summary

This thesis presents a comprehensive analysis of the transition from high-voltage SF6 circuit breakers to high-voltage vacuum interrupters (VIs) for 110 kV and higher, which play a critical role in modern transmission systems. The question arises whether existing customary quality assurance measures can be applied directly to these new interrupters. So far, manufacturers maintain that, thanks to stringent quality control and a proven design, all vacuum interrupters leaving the factory are sealed-for-life. The long-term functionality of a VI depends on maintaining an adequate vacuum level. Since direct pressure measurement is not feasible, this study employs the inverted magnetron method, which correlates ion current measurements with internal pressure. Analysis of the ion current waveform offers critical insights into the vacuum level, providing valuable information about the longevity and reliability of the vacuum interrupter. The physical lifespan of a vacuum interrupter (VI) is influenced by multiple factors, with the vacuum level inside the interrupter being particularly critical. Over time, gaseous molecules may infiltrate through tiny leaks, causing the internal pressure to increase gradually. As the pressure approaches a certain critical threshold, the VIs ability to withstand high voltage significantly decreases. This decline continues until reaching a minimum breakdown voltage, the Paschen Minimum, after which the breakdown voltage increases again. This behavior follows Paschen's law. The flat region on the left side of the curve indicates the breakdown voltage in unprocessed conditions, largely dictated by the surface condition of the internal components of the interrupter. Although this research focuses on one critical aspect of VI performance, it acknowledges that other failure mechanisms exist.