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In compressed gas insulated cable SFтВЖ has the gas pressure in the range of
10 to 20 mm-Hg
80 to 100 mm-Hg
3 to 5┬аkg/cm2
40 to 50┬аkg/cm2
3 to 5┬аkg/cm2
Sulfur Hexafluoride (SF6тАЛ) is used as an insulating medium in Gas Insulated Substations (GIS) and underground cables due to its high dielectric strength and excellent arc-quenching properties. In these applications, the gas is maintained at a specific pressure, typically between 3 to 5┬аkg/cm2, to achieve the required insulation level.
Sulfur Hexafluoride (SF6тАЛ) is used as an insulating medium in Gas Insulated Substations (GIS) and underground cables due to its high dielectric strength and excellent arc-quenching properties. In these applications, the gas is maintained at a specific pressure, typically between 3 to 5┬аkg/cm2, to achieve the required insulation level.
EbreakdownтАЛтИЭP
V=EтЛЕd
The insulating capability of SF6тАЛ is directly proportional to its gas density and pressure. By increasing the pressure to the 3тИТ5┬аkg/cm2 range, the molecules of SF6тАЛ become more tightly packed, significantly increasing the probability of electron attachment, which inhibits the formation of electron avalanches and prevents electrical breakdown.
SF6тАЛ is an electronegative gas with high affinity for free electrons.
The gas remains stable and inert at operating temperatures.
Pressure must be monitored to ensure it stays above the minimum required for dielectric integrity.
Higher pressure allows for more compact equipment design compared to air insulation.
High dielectric strength compared to air.
Superior arc extinction capabilities.
Chemical stability and non-flammability.
Allows for significant space savings in substations.
High global warming potential if leaked into the atmosphere.
Requires high-quality sealing to prevent gas loss.
Decomposition products can be corrosive if moisture is present.
Gas Insulated Switchgear (GIS).
Compressed Gas Insulated Cables (CGIC).
High voltage circuit breakers.
Gas-insulated transformers.
Typical operating pressure for GIS is around 3 to 5 bars or kg/cm┬▓. Variations may occur based on the specific voltage rating and manufacturer design.
Options A and B represent vacuum or near-atmospheric levels, which are insufficient for HV insulation requirements.
C is correct тАФ SF6 gas in compressed insulated cables is maintained at a pressure of 3 to 5 kg/cm┬▓ to ensure optimal dielectric strength.
Always remember that SF6тАЛ gas pressure is roughly proportional to the breakdown voltage; thus, pressure monitoring is a critical maintenance task in GIS substations.