A vacuum circuit breaker is a non-magnetic and low-maintenance circuit breaker that can be used in high-voltage circuits. Vacuum Circuit Breakers are designed to operate in harsh environments such as hot temperatures and high humidity. In this blog, we will discuss the functions of a vacuum breaker, its working principle, and how it is constructed.
What is a Vacuum Circuit Breaker?
A vacuum circuit breaker is a type of circuit breaker where the arc quenching occurs in a vacuum medium. Unlike oil or air circuit breakers, which use external mediums to extinguish the arc, VCBs rely on the high dielectric strength of a vacuum to interrupt current flow. This makes them highly effective for medium-voltage applications, typically ranging from 11 kV to 33 kV.
Types of Vacuum Circuit Breakers
Vacuum circuit breakers is used to interrupt the electrical power supply to the load when there is a short circuit or overload condition. It is an overcurrent device that trips when it detects a fault on the circuit. Vacuum breakers are mainly used as overcurrent protection devices in distribution panels and switchgear.
There are two types of vacuum circuit breakers:
- Thermal-type circuit breaker
- Magnetic-type circuit breaker
The thermal type works on a bimetallic principle, while the magnetic type contains a relay that opens when it detects current flow. The thermal type is one of the most common types of vacuum circuit breakers. This type of breaker uses a bimetallic strip to detect an overload condition on a circuit. The bimetallic strip is made up of two different metals, which expand at different rates when heated.
When the circuit breaker detects an overload condition, it heats up and expands. This expansion causes the bimetallic strip to bend. When it is bent far enough, it trips the breaker and stops the current flow.
Working Principle of Vacuum Circuit Breaker
The working of a vacuum circuit breaker is based on the principle of magnetic attraction and repulsion. It uses electromagnetism to open or close the contacts inside a vacuum tube, which makes it different from other circuit breakers used in power stations that use either electro-mechanical or hydraulic mechanisms. When there is an imbalance in pressure between the two sides, an air gap opens, interrupting current flow. Therefore, the valve is closed only when there is no voltage difference between the two poles; this ensures that it will not open prematurely.
The vacuum circuit breaker prevents short circuits and overloads from damaging equipment or starting fires. It is installed on the main power feed to an electrical panel and opens when there is a sudden change in voltage or current flow. Vacuum circuit breakers are used to protect electrical circuits from short circuits and overloads and are designed to withstand the high intensity of current in the event of a short circuit.
Construction of Vacuum Circuit Breaker
The vacuum circuit breakers are low in cost and free from maintenance and are designed to protect the equipment against the overcurrent in the power supply. The vacuum circuit breakers are made up of the vacuum switch, a sealed glass tube containing gas at high pressure. When an excess current flows through it, this gas gets ionized and suddenly becomes conductive due to electrostatic discharge or arc created between two electrodes inside these switches.
When this happens, the arc is extinguished by the pressure of the gas. These breakers are widely used in many industries, such as oil & gas, mining, power generation etc.
Opt for the premium quality circuit breakers
Vacuum circuit breakers are low in cost and free from maintenance. They are also safe for long-term operation. In addition, vacuum circuit breakers also have a reliable service life. All these factors make this equipment highly attractive to potential customers. One thing to keep in mind while investing in these breakers is that the supplier you choose plays a critical role in the life of the equipment. Therefore, we suggest going for reputable and known brands. After all, their product quality is unmatched.
Key Components of a VCB
1. Vacuum Interrupter – The heart of the VCB, containing fixed and moving contacts sealed within a vacuum chamber.
2. Operating Mechanism – A spring or solenoid-based mechanism that opens and closes the contacts.
3. Insulating Housing – Provides mechanical support and electrical insulation.
4. Terminal Connectors – Facilitate the connection of the breaker to the electrical system.
Advantages of Vacuum Circuit Breakers
1. High Dielectric Strength – The vacuum offers superior insulation, allowing for compact breaker designs.
2. Low Maintenance – Absence of oil or gas eliminates the need for frequent servicing.
3. Long Service Life – Minimal wear and tear due to fewer moving parts.
4. Fast Arc Extinction – Quick interruption of current reduces damage to the system.
5. Environmentally Friendly – No harmful gases or oils are used, making VCBs eco-friendly.
Applications of Vacuum Circuit Breakers
VCBs are widely used in: – Power distribution networks – Industrial plants – Railway electrification systems – Renewable energy installations – Commercial buildings
Comparison with Other Circuit Breakers
VCB vs. Oil Circuit Breaker (OCB) – VCB: No oil, hence no fire risk; faster operation. – OCB: Requires oil maintenance; slower arc quenching.
VCB vs. Air Circuit Breaker (ACB) – VCB: More compact; better for medium-voltage applications. – ACB: Suitable for low-voltage systems; bulkier design.
VCB vs. SF6 Circuit Breaker – VCB: No greenhouse gas emissions; simpler construction. – SF6 Breaker: Higher voltage handling but environmentally concerning.
Maintenance of Vacuum Circuit Breakers
Despite their low-maintenance nature, periodic checks are essential: – Inspect contacts for wear. – Verify mechanical operation. – Check insulation integrity. – Test dielectric strength periodically.
Future Trends in Vacuum Circuit Breaker Technology
Advancements in materials and design are enhancing VCB performance: – Smart VCBs: Integration with IoT for real-time monitoring. – Higher Voltage Ratings: Development of VCBs for ultra-high-voltage applications. – Eco-Friendly Designs: Further reduction in environmental impact.
Conclusion
Vacuum circuit breakers have revolutionized electrical protection systems with their efficiency, reliability, and compact design. Their ability to operate without external quenching mediums makes them ideal for modern power distribution networks. As technology advances, VCBs will continue to play a pivotal role in ensuring safe and uninterrupted power supply across various industries.
