Mechanical Stresses in GIS Grid components

This paper looks at how to design and improve circuit breakers that use Natural Origin Gas

(NOG) instead of SF₆ for insulating medium. NOG is less harmful to the environment and nontoxic, but it is technically challenging to use because it does not insulate as well as SF₆. To make it work, higher operating pressures are needed, which changes how GIS components must be designed, especially the actuation aimed to drive the switch function.

The suggested solution combines vacuum technology with pressurized NOG insulation. This takes advantage of vacuum interrupters' ability to stop electrical arcs while offering environmental benefits. However, this combination creates complex engineering challenges where the mechanisms that work at normal pressure meet those that operate under high pressure. The design must allow motion to pass through pressure barriers while ensuring reliability, reducing leaks, and maintaining steady performance throughout the equipment's life. Earlier studies created a smart actuation system that uses special bellow designs to handle pressure changes during the initial movement of the contacts, which is about 70% of their total movement. This design works well under different pressure conditions. However, the impact of the front wall—the steel plate that separates normal and pressurized areas—had not been thoroughly studied before.

This paper builds on that research by examining how the stiffness of the front wall affects movement performance through detailed experiments. A special prototype was made with better force measurement tools, including laser sensors and Linear Variable Differential

Transformers (LVDT) at key points. Initial simulations helped set up the experiments by identifying important measurement spots and expected patterns of deformation.

Laboratory tests looked at different operating conditions across various pressure levels (rated, design, and minimum functional pressures) and environmental factors like temperature changes and mechanical stress from switching. The results showed that the front wall's metal sheet significantly moved due to pressure increases and vibrations from switching.

The findings indicate that the front wall's deformation affects how the contacts move, leading to inconsistencies in switching. These mechanical changes can reduce the kinematic chain's effectiveness by altering movement patterns and closing forces. The combined effects of pressure and temperature create a complex situation that needs careful handling to ensure reliable circuit breaker performance.

Well structural design ensures that the kinematic chain works with consistent forces and movement characteristics, no matter the internal pressure or outside temperature. This improvement boosts overall GIS reliability and supports wider sustainability goals by enabling efficient SF₆-free switchgear designs that maintain operational excellence while meeting environmental standards and aiding the electrification needed to reduce global greenhouse gas emissions.