SF6 (sulfur hexafluoride) breaker is a type of circuit breaker that uses sulfur hexafluoride gas as the insulating and arc-quenching medium. SF6 is a highly stable, non-toxic, and non-flammable gas that has a much higher dielectric strength than air or other gases commonly used in circuit breakers. The SF6 breaker is well suited for high-voltage applications, such as in power transmission and distribution systems.
The gas filling pressure range for an SF6 (sulfur hexafluoride) circuit breaker is typically between 0.5 and 1.5 bar (7.25 to 21.75 psi) at 20 °C (68 °F). The exact pressure range can vary depending on the design of the breaker and the specific application.
The SF6 gas is usually filled into the breaker at the factory before it is shipped to the customer. The gas is stored in a high-pressure cylinder or tank and is introduced into the breaker through a filling valve. Once the breaker is filled with the SF6 gas, the filling valve is sealed and the pressure is monitored to ensure that it remains within the safe range.
It's important to note that SF6 is a greenhouse gas that can contribute to global warming if it leaks into the atmosphere, so SF6 breaker are designed to minimize gas leakage and use recovery systems to capture and recycle the SF6 gas. To avoid any leakage and also make sure that it is operating within the safe range, the pressure inside the breaker should be regularly monitored and maintained at the correct level.
SF6 Circuit Breaker internal parts
The internal parts of an SF6 (sulfur hexafluoride) circuit breaker include several key components that work together to interrupt the current flow and protect the electrical system:
Contacts: The contacts are the moving parts of the breaker that carry the current when the breaker is closed. They are typically made of copper or another conductive material and are designed to open and close quickly and reliably.
Arc chutes: The arc chutes are metal plates that are positioned between the contacts to guide and cool the arc as it forms when the breaker is opened. They are typically made of copper or another conductive material and are designed to dissipate the heat generated by the arc.
Arc runners: The arc runners are metal plates that are positioned on the side of the arc chutes to guide and cool the arc as it forms when the breaker is opened. They are typically made of copper or another conductive material and are designed to dissipate the heat generated by the arc.
Insulating housing: The insulating housing surrounds the contacts, arc chutes, and arc runners and is filled with SF6 gas. It is designed to protect the internal components from external environmental conditions and to provide insulation to the breaker.
Operating mechanism: The operating mechanism is the mechanism that controls the movement of the contacts. It is typically an electromechanical or pneumatic mechanism that is controlled by a control system.
Pressure and vacuum interlock: The pressure and vacuum interlock is a device that monitors the pressure of the SF6 gas in the breaker and opens or closes the breaker accordingly.
Gas leakage detector: The gas leakage detector is a device that monitors the SF6 gas leakage from the breaker and alarms if the leakage exceeds the acceptable level.
Gas handling unit: The gas handling unit is a device that is used to refill, maintain and recover SF6 gas.
These internal parts work together to ensure that the breaker can safely and reliably interrupt the current flow when necessary and to protect the electrical system from damage caused by overcurrents and short circuits.
SF6 Circuit Breaker Application
SF6 (sulfur hexafluoride) circuit breakers are primarily used in high-voltage power transmission and distribution systems, typically above 72.5 kV (kilovolts). They are also used in high-voltage substations and switchyards, as well as in some industrial and mining applications.
Some of the key advantages of SF6 circuit breakers include:
High reliability and long service life: SF6 breakers are designed to withstand high current and voltage levels and to operate for many years without requiring major maintenance or repair.
High-voltage insulation: SF6 gas has a much higher dielectric strength than air or other gases commonly used in circuit breakers, making it well suited for high-voltage applications.
Compact size: SF6 breakers are relatively compact, which makes them well suited for use in substations and switchyards where space is limited.
Low noise level: SF6 circuit breakers produce less noise than other types of circuit breakers, which makes them suitable for use in environments where noise levels must be kept low.
However, SF6 is a greenhouse gas that can contribute to global warming if it leaks into the atmosphere. To avoid any leakage and also make sure that it is operating within the safe range, the pressure inside the breaker should be regularly monitored and maintained at the correct level.