Electrical faults are one of the most problematic and damaging issues. They cause extensive and expensive downtimes. But to avoid all these issues, SF6 circuit breakers play an important role in instant stopping of high-voltage problems.
This blog will help you understand the functionality of SF6 circuit breakers, their benefits, as well as vital maintenance information to help ensure that power systems operate properly and safely. So, keep learning!
1) What Is an SF6 Circuit Breaker?
“An SF6 circuit breaker is a high-voltage electrical switchgear device that interrupts the flow of electricity using sulfur hexafluoride (SF6) gas during overloads or faults.”
To be simpler, an SF6 circuit breaker is essentially a device used for high-voltage electrical systems. It manages the current to reduce the risk of faults damaging the system. Basically, an SF6 circuit breaker uses SF6 gas (sulfur hexafluoride) as an insulator and arc-quenching medium.
Basic Properties of SF6 Gas
- Odourless, Colourless, and Non-Harmful: When handled appropriately, SF6 gas does not pose health risks, having no scent or colour.
- Unreactive with the Surrounding Environment: Its stability makes it safe and dependable for use in electrical systems, as it will not react easily with other substances.
- Efficient Arc Quenching: Due to its chemical properties, SF6 mitigates faults by interrupting the power supply and, thus, protecting equipment.
- Arc Cooling: This feature assists by cooling the electrical arc, which improves system safety and protection.
- Superior Density and Insulation: Compared to other gases, SF6 has superior insulation and retains its density even under lower pressures.
- Useful in Extremely Hot or Cold Temperatures: Whether exposed to extreme heat or cold, SF6 maintains these qualities, which assist outdoors and in other extreme conditions.
- Effective Insulator for High Voltage Circuit Breakers: SF6 is often incorporated in circuit breakers working under severe or high voltage conditions due to its capability to restrain arc and insulate efficiently.
2) Basic structure of SF6 circuit breaker
An SF6 circuit breaker has some basic components which control and stop the flow of current. Each component is critical to the SF6 Gas Circuit Breaker for proper and safe functioning.
i) Interrupter Unit: This is the most important unit, which closes or opens the circuit. It has the contacts that lead the current. At fault, the contacts open, and SF6 gas is let out to extinguish the arc. The interrupter unit has the ability to withstand high voltage and current.
ii) Fixed and Moving Contacts: In SF6 breakers, the fixed and moving contacts serve an important role as components for interrupting electricity flow during fault conditions. The fixed contact is the arcing horn, and the moving contact is also a hollow cylinder having rectangular openings for gas to flow.
These contacts are put in a chamber which is filled with SF6 gas, which quenches the arc produced.
iii) Arc Quenching Chamber: An arc quenching chamber is a specific part found in circuit breakers, which is used to extinguish electrical arcs that form during or after interruption of highly energised circuits. The arc quenching chamber helps extinguish the arc by the separation of the contacts.
iv) SF6 Gas Tank: The SF6 gas under pressure is stored within this sealed tank. It prevents leakage and protects the gas from contamination. The tank is built strong to bear pressure as well as other environmental factors.
v) Operating Mechanism: This controls the movement of the contacts. This is spring-operated, hydraulic, or motorised, which ensures the breaker is opened and closed within the required time.
3) SF6 Circuit Breaker Types
There are two ways to group SF6 circuit breakers: one is based on the arc quenching mechanism, and the other is based on the installation design. Let’s analyse both types, so go ahead!
Based on the Arc Quenching Mechanism
These types explain the role of SF6 gas in extinguishing the electric arc during current interruption.
a) Non-Puffer Type: This is the older version. It employs a simple piston or valve that pours SF6 gas over the arcing zone. It’s very inefficient because it releases the SF6 gas directly over the arc without compressing it first. So, it is rarely used now.
b) Single-Pressure Puffer Type: This is the most common type. It employs a “puffer” cylinder that compresses SF6 gas into a spray that crosses the arc. The forceful flow of gas rapidly cools the arc, which then may be extinguished.
c) Double-Pressure Type: In this type, SF6 gas is kept in a high-pressure tank. Then, during operation, it is injected into a low-pressure chamber. It’s mostly used in very high voltage systems because it is able to store a lot of energy, but it is complicated and expensive.
Based on Installation Design
Such types emphasise the location and positioning of the breaker in a substation. Let’s discuss them.
a) Dead Tank Type: The interrupter is located within a grounded metal tank. This makes the device safer for maintenance. Well, it is commonly used in substations.
b) Live Tank Type: Here, the interruptor unit is ungrounded and is at high voltage. The device is lighter in weight, which makes it suited for outdoor uses because space and supporting structures are limited.
c) GIS Type (Gas Insulated Switchgear): All parts are placed in a compact sealed enclosure, which is filled with SF6 gas. It saves space, which is perfect for urban areas.
4) How does an SF6 circuit breaker work
You know Sulfur hexafluoride (SF6) gas is used to inhibit electricity flow in circuit breakers sf6 during any fault to save the equipment from damage. Now, let’s discuss how SF6 circuit breaker works, so keep in touch!
Typically, the circuit breaker contacts are closed during normal operating conditions. Once the error or fault occurs within the system, the circuit breaker contacts will be pulled apart separately & an arc is struck between them.
The SF6 gas draws the free electrons in the path of the arc to form ions, where these ions will not behave as charge carriers. This is because these ions will serve to be the dielectric strength-enhancing component of the SF6 gas, thus extinguishing the arc. Thus, this process reduces the pressure to 3kg/cm^2, so this gas can be stored in a weak-pressure chamber.
This weak pressure SF6 gas is better pulled back to the chamber for reuse. The puffer piston power is now primarily required for the quenching of the arc during the opening stroke due to the closed piston attached to the moving contacts.
5) Common Application Scenarios
This particular type of breaker can be found in many important places around the world because of its safety and reliability. Let us analyse where and why they are applied.
- High-Voltage Power Stations
In high-voltage power stations, SF6 circuit breakers are used. These stations manage vast quantities of electric power. Moreover, SF6 breakers manage the system’s control and protection during faults and overloads.
- Electrical Substations
In substations, transformers and other important equipment are guarded by SF6 breakers. They interrupt the circuit rapidly to prevent damage and enhance safety.
- Power Transmission Networks
They are utilised along lines which transmit electricity over long distances. Moreover, SF6 breakers ensure the proper and safe flow of power.
- Industrial Plants
Industrial plants and large factories utilise SF6 circuit breakers to meet the demand of their heavy power consumption. They safeguard motors, machines, and other high-power devices.
- Renewable Energy Systems
SF6 circuit breakers are also applied in solar and wind farms. They assist in power regulation and maintaining the stability of the system.
6) SF6 Circuit Breakers Advantages and Disadvantages
The fast and reliable action of SF6 breakers makes them popular in modern power systems. Like any equipment, SF6 circuit breakers also have some advantages and disadvantages, it is important for you to know about them. Let’s move forward!
SF6 circuit breaker Advantages
+ High Efficiency: SF6 circuit breakers have higher efficiency than most other breakers because SF6 safely and quickly break high-voltage currents.
+ Excellent Insulation: SF6 circuit breaker has strong insulation. It keeps the system safe from electrical arcs.
+ Low Maintenance: These breakers are kept in good condition because the gas prevents the system from damage or wear.
+ Compact Size: The high insulating strength of SF6 allows the equipment to be smaller in size, so it saves space.
+ Reliable Operation: SF6 circuit breakers are reliable and strong. These breakers work well in a variety of weather and environmental conditions.
SF6 circuit breaker Disadvantages
– Environmentally Harmful: If it leaks, SF6 can be extremely damaging to the environment.
– Costly: If we compare the SG6 circuit breaker to some other types, the purchase and installation costs of SF6 are remarkably higher.
– Safety Issues: SF6 gas needs to be handled, stored, and disposed of with extreme caution.
– Risk of Leakage: If the gas escapes, it decreases the system’s performance and overall safety of the breaker.
7) Essential Maintenance Practices for SF6 Circuit Breakers
Well, maintenance of SF6 circuit breakers must be done to ensure operational safety and reliability. Proper maintenance of the equipment helps in preventing equipment and system failures, and it can enhance the lifespan of the equipment. Let’s discuss them:
- Gas Pressure Check: The SF6 gas must be maintained at the correct pressure value. This is because high or low pressure could create problems with efficiency. So, the fire and gas pressure gauges should be regularly checked to avoid any problems.
- Leak Detection: You should use the leak detectors to detect any leakage in the system. If you do not give attention towards its maintenance, it can become a hazard to the breaker.
- Contact Inspection: The breaker contacts are subjected to wear and tear over their lifecycle. So, you should properly inspect the contacts. If you detect any sign of damage or erosion, then contacts should be restored or replaced.
- Insulation Testing: Test the insulation of the different parts of the breaker for safety. It helps reduce internal flashovers or blowups.
- Cleaning: The dust and dirt particles can accumulate on the exterior nozzles and the other external parts of the equipment. So, you should clean the equipment regularly to remove the dust and dirt.
- Operation Test: You should manually operate the breaker and check the movement of all the mechanical components. This will ensure the circuit breaker will function correctly in the case of real faults.
8) SF6 Circuit Breaker VS Vacuum Circuit Breaker
SF6 and vacuum circuit breakers are commonly used in power systems. Each type has advantages that make it suitable for specific applications. Let’s discuss them:
- Arc Quenching Method
SF6 circuit breaker: SF6 breakers extinguish the arc using sulfur hexafluoride gas. It provides excellent cooling and insulation.
Vacuum circuit breaker: It interrupts the arc within a vacuum chamber. The absence of air allows the arc to quickly extinguish.
- Voltage Level
SF6 Circuit Breaker: SF6 circuit breakers work efficiently at high and extra high voltages, usually greater than 66kV. They are used for the transmission network, in large substations, and in intensive industrial applications.
Vacuum Circuit Breaker: Vacuum circuit breakers are highly efficient for medium voltage equipment, generally up to 36kV. These devices find application in office buildings, small substations, and medium-sized industrial plants.
- Maintenance
SF6 circuit breaker: The Routine gas checks and leak inspections are crucial for SF6 breakers.
Vacuum circuit breaker: It requires less maintenance it is because it has sealed chambers.
- Environmental Impact
SF6 circuit breaker: The release of SF6 gas is harmful as it is a highly potent greenhouse gas.
Vacuum circuit breaker: No harmful gases are emitted by vacuum breakers.
- Lifespan
SF6 circuit breaker: SF6 breakers will require more frequent servicing.
Vacuum circuit breaker: Due to minimal wear, vacuum breakers enjoy a longer service life.
9) SF6 Circuit Breaker FAQ
1. What is SF6 used for?
SF6 is used in high-voltage circuit breakers as an insulating medium and for quenching the arc.
2. What are the disadvantages of SF6?
SF6 can be a severe greenhouse gas that leaks from industrial applications. In addition, it requires special care during its storage and use processes. Therefore, SF6 is environmentally hazardous.
3. Is SF6 being phased out?
Yes, there are currently ongoing projects targeting the reduction of SF6 use, as well as finding SF6-free alternatives to eco-sensitive electric equipment.
4. Why use SF6 gas in a circuit breaker?
SF6 is exceptional in its insulating capabilities and ability to put out arcs. Because it significantly improves the safety and reliability of breakers by rapidly stopping electrical faults.
10) Conclusion
So, we saw that SF6 circuit breakers are crucial for the protection of modern electrical systems. Breakers will rapidly and safely stop electrical faults with the help of SF6, which acts as an excellent insulator and arc-quenching gas. Moreover, these breakers offer the advantages of low maintenance and long-lasting reliability. SF6 must be handled with care due to the gas’s environmental consequences.
Here, one important thing to share with you is that for high-quality and dependable circuit breakers, you should trust VCB Breaker products. Our equipment is purpose-built to deliver safety and efficiency for demanding long-term high-voltage power system applications. You can contact us right now just by clicking here.
