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Sulphur hexafluoride cable is insulated by
Impregnated paper
Polyvinyl chloride
High pressure oil
Compressed gas
Compressed gas
Sulphur hexafluoride (SF6тАЛ) cables utilize compressed SF6тАЛ gas as the primary dielectric insulating medium. The gas is maintained at high pressure within the cable sheath to provide high dielectric strength and excellent arc-quenching capabilities.
Sulphur hexafluoride (SF6тАЛ) cables utilize compressed SF6тАЛ gas as the primary dielectric insulating medium. The gas is maintained at high pressure within the cable sheath to provide high dielectric strength and excellent arc-quenching capabilities.
VbтАЛ=f(p├Чd) тАФ Paschen's Law describing the breakdown voltage as a function of pressure and gap distance
╬▒тЙИ╬╖ тАФ The condition for electrical breakdown where ionization rate equals attachment rate
The insulation mechanism relies on the electronegative nature of SF6тАЛ gas. Molecules of SF6тАЛ capture free electrons to form heavy, low-mobility negative ions, effectively suppressing the development of electron avalanches. By pressurizing the gas, the density of these molecules increases, significantly elevating the breakdown voltage strength of the insulating gap according to Paschen's Law.
SF6тАЛ is an inert, non-toxic, and non-flammable gas.
It exhibits high dielectric strength, approximately 2.5 to 3 times that of air at the same pressure.
The gas remains chemically stable even at high temperatures encountered during heavy load conditions.
Commonly used in Gas Insulated Substations (GIS) and EHV transmission lines.
Superior heat dissipation compared to solid insulation
High dielectric strength allowing for compact cable design
Non-aging property of the gas insulation
Excellent arc extinguishing properties
Requires high-pressure containment vessels and sealing
Susceptible to gas leakage, necessitating monitoring systems
SF6тАЛ is a potent greenhouse gas requiring strict environmental handling
High cost of gas and specialized infrastructure
EHV Underground transmission lines
Gas Insulated Lines (GIL)
High-voltage test laboratories
| Feature | Conventional Cable | Gas Insulated Cable |
|---|---|---|
Insulation Type | Solid (Paper/XLPE) | Gas (SF6тАЛ) |
The breakdown voltage of SF6тАЛ is highly sensitive to the uniformity of the electric field and the surface finish of the conductors.
Option A (Impregnated paper) is used in Mass Impregnated (MI) cables; Option B (PVC) is used for low voltage insulation; Option C (High pressure oil) is used in Oil-Filled (OF) cables.
D is correct тАФ Sulphur hexafluoride (SF6тАЛ) cables are insulated using compressed gas, which provides superior dielectric performance for high-voltage applications.
Always remember that SF6тАЛ is effectively used in both cables (GIL) and circuit breakers due to its unique electron-attachment capability which rapidly restores dielectric strength after fault clearing.