Improving the accuracy of SF6 leakage detection for high voltage switchgear

Even though average leakage rates of SF₆ in high voltage equipment are very low, there is no guarantee for a 100% leakage-free system, especially when considering the generally long lifespan of high-voltage equipment. Taking in view the rather strict maximum allowed leakage rate of SF₆ per year, regulated by international standards, these facilities should be equipped with suitable monitoring devices. However, accurate detection of low rates of gas leakage is not an easy task. This paper sheds light on the challenges of leakage detection by thorough analysis of physical aspects. Furthermore, it proposes two methods for high-fidelity leakage monitoring and detection with special emphasis on their suitability for use in substations. Application of these methods in the laboratory environment revealed an accuracy of detection levels of 0.3% per year. This is a substantial improvement from the present monitoring systems that show fluctuation levels of the indicator to be as high as up to several percent, which is clearly above the acceptable level.