7 Core Reasons Why SF6 Is Choice For Gas Insulated Switchgear

Gas insulated switchgear (GIS) plays a crucial role in modern power systems, and sulfur hexafluoride (SF6) gas accounts for a significant portion of this application due to its properties. This article will delve into the seven core advantages of SF6 gas in GIS applications.

Reasons To Choose Sf6 For Gas-Insulated Switchgear

Excellent Insulation Performance

SF6 gas insulated switchgear manufacturers tell you,SF6 has a very high dielectric strength, about three times that of air under the same pressure, which can effectively reduce the size of electrical equipment and improve insulation reliability.

Compared to traditional air-insulated substations (AIS) that require large bays and numerous insulators, GIS can enclose the entire substation (such as circuit breakers, disconnectors, grounding switches, and instrument transformers) within a grounded metal casing filled with pressurized SF6 gas. This allows GIS to occupy only 10% to 25% of the land area of ​​AIS, making it ideal for land-scarce cities, underground facilities, mountainous areas, and harsh environments.

Efficient Arc Extinguishing Capability

In Gas Insulated Switchgear, SF6 can interrupt fault currents of tens of thousands of amperes within milliseconds, significantly improving the safety level of the power grid.

SF6 gas possesses unparalleled arc-extinguishing capabilities, primarily due to its two unique physicochemical properties:

Strong Electronegativity: SF6 molecules have an extremely strong ability to adsorb free electrons. These free electrons are the conductive medium in an electric arc. SF6 rapidly captures electrons to form negative ions, and the movement speed of these negative ions is much slower than that of free electrons. This directly leads to a sharp decrease in the conductivity of the arc medium, thus rapidly extinguishing the arc.

Thermochemical Properties: At the high temperature of an electric arc, SF6 decomposes and absorbs a large amount of heat, simultaneously producing decomposition products with excellent insulation and arc-extinguishing properties. When the current crosses zero, these products can quickly recombine into the original SF6 molecules, restoring the insulating strength of the medium and preventing arc reignition.

SF6 circuit breakers can interrupt short-circuit currents with significantly higher efficiency and speed than other types of circuit breakers, ensuring power grid safety.

Stable Chemical Properties

At normal temperature and pressure, SF6 is a colorless, odorless, non-toxic, and non-flammable inert gas. It does not react with most substances, including metals and insulating materials, exhibiting excellent chemical stability.

This stability ensures that the internal structure of GIS equipment will not corrode or age due to the gas’s chemical reactions during long-term operation, thus guaranteeing a service life of decades and extremely low maintenance requirements.

Low Operating Pressure

Due to the extremely high dielectric strength of SF6, GIS equipment requires relatively low SF6 gas operating pressures (typically between 0.4 and 0.6 MPa absolute pressure) to achieve the required insulation levels. This lower operating pressure offers several advantages:
It reduces the requirements for the sealing system, decreasing the risk of gas leakage.
It reduces the mechanical burden on the metal casing, resulting in a lighter and more compact equipment structure with lower manufacturing costs.
It simplifies operation during maintenance and gas replenishment.

Excellent Thermal Conductivity

SF6 gas exhibits superior thermal conductivity compared to air, especially under convection conditions. In GIS equipment, the flow of current through conductors generates heat. SF6 gas effectively transfers this heat from the conductors to the cooler outer casing, which is then dissipated into the external environment.

This efficient heat dissipation helps prevent localized overheating of the equipment, maintains the performance of the insulation materials, and thus improves the current-carrying capacity and long-term operational reliability of the equipment.

Unique Self-Healing Properties

The gas molecules decomposed under the action of electric arc can automatically recombine and regenerate in a short time (10^-6~10^-7 seconds), maintaining stable insulation performance.

Excellent Non-Corrosiveness

High-quality SF6 gas itself, and its decomposition products under normal operating conditions, are non-corrosive to the metals (such as aluminum and copper) and insulating materials (such as epoxy resin) used inside the GIS.

By strictly controlling the moisture content in the gas (usually achieved through built-in adsorbents), the formation of corrosive acidic substances (such as HF) due to moisture can be avoided. This characteristic fundamentally protects the integrity of the internal structure of the equipment and is a key prerequisite for the long lifespan and maintenance-free operation of GIS.

FAQ

What Is SF6 Gis Switchgear？

This is a compact high-voltage power distribution unit that uses SF6 as the insulating medium, sealing components such as circuit breakers and disconnectors within an air-filled compartment.

What Is The Purpose Of Gas Insulated Switchgear?

By optimizing the spatial layout, the high-voltage power distribution equipment can be miniaturized, while improving power supply reliability and environmental adaptability.

Why Is Sf6 A Good Insulator?

Because its highly electronegative molecular structure can efficiently capture free electrons and suppress the development of discharge phenomena.

Is Sf6 Gas Safe?

The pure product is non-toxic and non-flammable, but it must be handled in a standardized manner to avoid the generation of decomposition products, and gas recovery must be strictly managed to reduce the greenhouse effect.

How Long Can Gis Gas-Insulated Switchgear Last?

Through strict process control and sealing design, modern GIS equipment can maintain stable operation for more than 30 years without maintenance.

Conclusion

SF6 gas, with its comprehensive performance advantages, has become an ideal choice for medium and high voltage GIS equipment, demonstrating irreplaceable value in ensuring power grid safety, compactness, and intelligence.

Take action now and let professional GIS solutions power your power network with reliable performance!