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Which gas is used in gas insulated substation?
Nitrogen + SF6тАЛ
Hydrogen + SF6тАЛ
SF6тАЛ
None of above
SF6тАЛ
Sulfur Hexafluoride (SF6тАЛ) is the standard gas used as an insulating and arc-quenching medium in Gas Insulated Substations (GIS). It is an inert, non-toxic, and heavy electronegative gas that provides superior dielectric strength compared to air.
Sulfur Hexafluoride (SF6тАЛ) is the standard gas used as an insulating and arc-quenching medium in Gas Insulated Substations (GIS). It is an inert, non-toxic, and heavy electronegative gas that provides superior dielectric strength compared to air.
EbтАЛтИЭPn тАФ where EbтАЛ is the breakdown strength and P is the gas pressure.
╬▒тИТ╬╖=0 тАФ the condition for the limiting dielectric strength of an electronegative gas.
The electronegative property of SF6тАЛ allows it to capture free electrons effectively, converting them into heavy, slow-moving negative ions. This process rapidly reduces the energy of the electron avalanche during a potential discharge, significantly increasing the breakdown voltage of the insulation gap. In circuit breakers, the high thermal conductivity of SF6тАЛ assists in rapid cooling of the arc path, facilitating arc extinction.
SF6 is approximately 5 times denser than air.
It exhibits excellent arc quenching capabilities due to its high electronegativity.
The gas is chemically inert and thermally stable up to 500┬░C.
GIS allows for a significantly smaller substation footprint compared to Air Insulated Substations (AIS).
High dielectric strength
Excellent arc quenching properties
Compact design and space-saving
Resistance to environmental contamination
High Global Warming Potential (GWP)
Requires high pressure containment vessels
By-products formed during arcing (e.g., SF4тАЛ, SO2тАЛF2тАЛ) can be toxic
High-voltage gas-insulated switchgear (GIS)
Gas-insulated transmission lines (GIL)
High-voltage circuit breakers
Gas-insulated transformers
Pure SF6тАЛ is standard; mixtures with N2тАЛ (Nitrogen) are sometimes used in extremely cold climates to prevent liquefaction.
Option A (Nitrogen + SF6тАЛ) is used only for specific temperature-limited applications, but pure SF6тАЛ is the primary answer for general GIS usage.
C is correct тАФ SF6тАЛ is the industry-standard gas used for insulation and arc quenching in gas-insulated substations.
Always remember that SF6тАЛ is a potent greenhouse gas, and current research focuses on eco-friendly alternatives like g3 or Novec4710 mixtures.