HV vacuum circuit breaker in GIS

Requirements for Larger Tank Enclosure in VCB

1. Vacuum breakers permit the use of insulation media other than SF6. When insulating gases such as dry air, nitrogen, or CO2 are chosen, their insulation performance will be inferior compared to that of SF6 at the same pressure.
2. Stray capacitances to the tank negatively impact voltage division within the vacuum interrupter (VI). This may necessitate a larger, higher - rated - voltage VI.

Considerations When Applying VCB in GIS

• Stray capacitances from the VI (primarily the shield) to the vessel cause an inhomogeneous voltage distribution.
• The reduced distance to ground results in higher electric field stress within the vacuum interrupter.
• The bellows must operate against high - pressure gas, increasing the drive energy and subjecting the bellows to greater mechanical stress.
• Due to encapsulation, heat exchange to the outside is more pronounced for VCB, leading to increased copper stem diameters.
• The length of the VI can be smaller than that of an SF6 interrupter.
• The insulating gas of VCB can be selected independently.
• The GIS enclosures (except for cast aluminum ones) will mitigate X - ray effects to the outside.