Vacuum circuit breakers are widely used in high-voltage switchgear, leveraging vacuum as the arc-extinguishing and insulating medium within a sealed vacuum container. Since their introduction in the early 1960s, advancements in key processes, the development of new arc chambers, and improvements in operating mechanisms have significantly enhanced their technical parameters. These circuit breakers, known for their excellent performance and reliability, have become increasingly prevalent in high-voltage switchgear applications.
Below is an overview of the advantages and disadvantages of vacuum circuit breakers:
Sealed Arc Chamber:
The arc extinguishes within a sealed container, preventing exposure to arc or hot gases. The arc chamber is designed as a standalone component, making installation and maintenance simple.
Compact Contact Gap:
The contact gap is small (around 10mm), requiring less closing force, simplifying the mechanism, and extending the service life.
Efficient Arc Extinguishing:
With a short arc-extinguishing time, low arc voltage, minimal energy loss, and reduced contact wear, vacuum circuit breakers support numerous switching operations.
Low Inertia:
The lightweight moving guide rod allows for frequent use.
Compact and Lightweight Design:
The operating mechanism is minimal, resulting in a smaller and lighter overall device.
Low Power Consumption and Noise:
Operating the switch requires little control power, and it generates minimal noise during operation.
Safety:
These breakers are oil-free, eliminating the risk of explosion or fire hazards, ensuring safe operation.
Durability and Stability:
The sealed structure prevents performance degradation caused by moisture, dust, or harmful gases, ensuring reliable and consistent operation.
Rapid Recovery:
After the arc is extinguished, the insulating medium between the contacts quickly recovers without needing replacement.
Low Maintenance Requirements:
The components, including the contact ring, do not degrade and require no replacement. Maintenance intervals can extend up to 20 years, and maintenance costs are about 1/20th of those for oil-less circuit breakers.
Reclosing Capability:
Vacuum circuit breakers can handle multiple reclosing operations, making them ideal for distribution network applications.
Overvoltage Risk:
Switching inductive or capacitive loads can cause overvoltage due to phenomena like current chopping or re-ignition. Adequate overvoltage protection is necessary.
High Initial Cost:
The specialized production of vacuum interrupters and the reliability of the mechanism result in a higher upfront cost. However, considering long-term operational and maintenance savings, the overall cost-effectiveness is favorable.
Contact Bouncing Issues:
The docking-type contact structure and spring-based operating mechanism may lead to:
Vacuum circuit breakers are predominantly used in indoor high-voltage switchgear, such as 12kV, 24kV, and 36kV VS1 mid-mounted switchgear. They are a critical component in ensuring reliable, safe, and efficient operation within power distribution systems.