SF6 Circuit Breaker Operation

SF6 Circuit Breaker

Operation Principle

• SF6 circuit breaker uses Sulphur Hexafluoride (SF6) gas as the insulating and arc quenching medium
• The breaker consists of fixed and moving contacts, arc shields, and a gas system
• When the breaker is closed, the moving contact touches the fixed contact, allowing current to flow
• When the breaker is opened, the moving contact separates from the fixed contact, creating an arc
• The SF6 gas is used to quench the arc, allowing the breaker to extinguish the fault current

Arc Quenching

• Arc quenching is the process of extinguishing the electrical arc that forms when the circuit breaker is opened
• SF6 gas has excellent arc quenching properties due to its high dielectric strength and ability to absorb free electrons
• The SF6 gas is released from the arc chamber and flows through the nozzle, creating a high-velocity gas flow that cools the arc and extinguishes it
• The arc quenching process is facilitated by the use of arc shields, which help to constrict the arc and increase the gas flow velocity

Advantages

• High dielectric strength, allowing for compact design and reduced size
• Excellent arc quenching properties, enabling fast and reliable fault current interruption
• Low maintenance requirements due to the closed gas system and lack of moving parts
• High reliability and long lifespan
• Environmentally friendly, as SF6 is a non-toxic and non-flammable gas

Limitations

• SF6 is a potent greenhouse gas, with a global warming potential (GWP) of 22,800
• SF6 circuit breakers are generally more expensive than air-blast or oil-filled circuit breakers
• Specialized equipment and training are required for handling and maintenance
• SF6 gas can be contaminated by moisture and air, reducing its effectiveness and requiring regular testing and maintenance

Gas Handling

• SF6 gas is stored in cylinders or gas carts
• Gas handling equipment, such as gas reclaimers and filling devices, are used to handle and manage the SF6 gas
• Regular gas testing and analysis are required to ensure the gas meets the required purity and moisture levels
• SF6 gas must be handled and stored according to safety guidelines and regulations to prevent accidents and environmental harm

SF6 Circuit Breaker

Operation Principle

• SF6 gas is used as insulating and arc quenching medium in SF6 circuit breakers
• Breaker consists of fixed and moving contacts, arc shields, and a gas system
• Closing the breaker allows current to flow, while opening it creates an arc that is quenched by SF6 gas

Arc Quenching

• Arc quenching is the process of extinguishing the electrical arc when the circuit breaker is opened
• SF6 gas has high dielectric strength and absorbs free electrons, making it an excellent arc quenching medium
• High-velocity gas flow cools and extinguishes the arc
• Arc shields constrict the arc and increase gas flow velocity to facilitate quenching

Advantages

• High dielectric strength allows for compact design and reduced size
• Fast and reliable fault current interruption due to excellent arc quenching properties
• Low maintenance requirements due to closed gas system and lack of moving parts
• High reliability and long lifespan
• Environmentally friendly due to non-toxic and non-flammable properties of SF6 gas

Limitations

• SF6 is a potent greenhouse gas with a global warming potential (GWP) of 22,800
• SF6 circuit breakers are generally more expensive than air-blast or oil-filled circuit breakers
• Specialized equipment and training required for handling and maintenance
• SF6 gas can be contaminated by moisture and air, reducing its effectiveness

Gas Handling

• SF6 gas is stored in cylinders or gas carts
• Gas handling equipment, such as gas reclaimers and filling devices, are used to handle and manage SF6 gas
• Regular gas testing and analysis are required to ensure gas meets required purity and moisture levels
• SF6 gas must be handled and stored according to safety guidelines and regulations to prevent accidents and environmental harm