Improved Sealing Technology for Switchgear with alternative Gases

In some previous work published in 2025 at the CIGRE International Symposium in Montreal,

Canada, a new patented elastomer sealing design demonstrated significative leakage rate reduction by specifically addressing CO2 permeation.

This paper is the follow-up of that study, with the test of complete representative GIS compartments using new and legacy sealings. The test was performed with the same methodology, based on the continuous monitoring of the inner gas pressure with the prototypes in a climatic chamber. The results are conclusive and very satisfactory, with a clear tightness improvement with the new sealings at 50°C and 20°C. The leakage rates were approximately reduced by a factor 3. No tests were performed at negative temperatures, but previous results showed that it was not critical down to -25°C at least. At 20°C, the new solution had an annualized leakage rate below 0.2%/year despite the small gas volume and high number of accessories (72.5 kV disconnector-earthing switch). Simpler and/or larger 72.5 kV GIS gas compartments and 145-170 kV GIS should have even better results.

Several challenges had to be addressed to implement this new solution, as the high standardization level also mean that many parts were common. The transition has already been applied to 72.5 kV and 145 kV SF6-free GIS. The SF6 versions will follow soon, with even better SF6 tightness. New products will already include this new solution. Other high-voltage products also started the transition to this sealing system (245-420 kV GIS, AIS, etc.).