Vacuum circuit breakers are a type of key switching device used in power systems. They can quickly cut off current when a circuit fails, effectively protecting the safety of circuits and related equipment. This article will deeply analyze the working principle, design features, and main application areas of vacuum circuit breakers, helping you to fully understand the importance and selection skills of vacuum circuit breakers in power systems.
What is a vacuum circuit breaker?
It is a high-efficiency switching device that has a wide application in power systems. It can quickly cut off the current when a fault occurs in the circuit to protect the circuit and the relevant equipment from damage. The core feature of this lies in the use of vacuum as insulation and arc extinguishing medium; hence, it is also called a vacuum arc extinguishing circuit breaker.
Working principle of vacuum circuit breaker
The principal working principle of a VCB is to interrupt arc energy between the contacts. Arcing occurs when the moving contact and the stationary contact separate in a vacuum environment. Due to rapid condensation of ions and metal vapor, the arc will be extinguished in a very short time. It increases the dielectric strength so high that the circuit breaker will be able to cut off the current quickly for safe operations of the power system.
Characteristics of vacuum circuit breaker
Higher insulation performance: Insulating media is vacuum, and arc extinguishing performance of a vacuum is equivalent to air and SF6 circuit breaker.
Compact design and light weight: As compared to conventional circuit breakers, vacuum circuit breakers have a compact design and flexible and easy installation.
Efficient and economical: No expensive maintenance is required, and they are very long-lasting with multiple full-capacity interruptions allowed.
Arcing time: Generally, it is about half a cycle (10ms), whatever the current size.
Noise level: Very low noise during operation; hence, it suits even noise-sensitive environments.
Long mechanical life: contact wear is small and can bear high-frequency operations.
Main components of vacuum circuit breaker
Vacuum arc extinguisher: the core component is used for arc isolation and extinction.
Moving contacts and stationary contacts: main electrical connection parts, usually made of highly conductive and wear-resistant materials.
Operating mechanism: to control the opening/closing of the circuit breaker, including a spring energy storage device that can be controlled manually or remotely.
Insulating Support: It provides mechanical support and electrical insulation.
Conductive connectors: Ensure the reliable connection of the circuit.
Housing: Protects internal parts from the environment.
Application of vacuum circuit breaker
Nowadays, vacuum circuit breakers are applied to each power system from 11kV to 33kV in substation, industrial power distribution and urban power grid. And its advantages are as follows:
Less maintenance: Because the contacts are in a vacuum condition, no regular maintenance is required.
Long life: up to thousands of times of rated current operations with high reliability.
Environmental protection: no gas emission, green environmental protection.
High compatibility: applicable for breaking high voltage power grid and capacitor load.
Selection skills
While choosing a vacuum circuit breaker, the following should be considered:
Rated current: according to actual load current, choose a proper specification, such as 630A, 1250A, etc.
Rated breaking current: The peak value of the short-circuit current should be withstood by a circuit breaker.
Installation environment: According to different indoor or outdoor applications, such as “N” for indoor installation and “W” for outdoor installation, the right model should be selected.
Switchgear type: According to the requirements of fixed or removable switchgear.
For example, when the maximum short-circuit current is 26kA, a circuit breaker with a rated breaking current of 31.5kA can be selected.
High voltage vacuum circuit breaker operating mechanism
The operating mechanism of the high-voltage vacuum circuit breaker drives the moving contacts and static contacts to separate through the energy stored in the spring. In a highly vacuum environment, the arc extinguishes rapidly because there is not enough gas to maintain the arc. Through this design, the circuit breaker can work efficiently under high voltage with less abrasion on the equipment.
Maintenance and Future Development
Maintenance points:
Regular checking of vacuum degree, integrity of wear, and appearance of contacts.
Ensure flexibility and reliability in operating mechanism.
Future trends:
The vacuum circuit breaker has a vital role in effective energy management for sustainable development during the period when smart grid and renewable energy sources will become more popular. The design will also be intelligent to meet changed power needs.
Conclusion
The vacuum circuit breaker has become an important device in the modern power system due to its high efficiency, safety, and low maintenance. It ensures not only excellent performance in the stability of a power system but also lays a very solid foundation for using intelligent and environmentally friendly power equipment.
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