This paper provides an in-depth overview of the working principle, main structure, and key characteristics of vacuum circuit breakers. It also explores the practical application of these devices in substation environments, highlighting their advantages, disadvantages, common faults, and corresponding troubleshooting methods. The findings serve as a reference for the operation and maintenance of vacuum circuit breakers, helping to ensure safe and efficient power system performance.
Keywords: vacuum circuit breaker, principle, structural characteristics, fault, treatment method
1. Introduction
In modern power systems, various components such as transformers and transmission lines must be connected or disconnected during maintenance, operational changes, or fault conditions. This requires reliable switching equipment that can quickly isolate faulty circuits, maintain system stability, and protect personnel during maintenance. Among these devices, the circuit breaker plays a critical role due to its ability to interrupt large fault currents and ensure system reliability. High-voltage circuit breakers are especially important, as they are responsible for maintaining the integrity of the electrical network under both normal and abnormal conditions.
A high-voltage circuit breaker is a critical device used to open and close circuits under normal conditions and automatically interrupt fault currents when necessary. Its primary requirements include sufficient breaking capacity, fast response time, and high reliability. One of the most crucial functions of a circuit breaker is arc extinction, which is achieved through specialized arc quenching mechanisms. Based on the medium used for arc extinction, circuit breakers can be classified into several types, including oil, air, SF6, vacuum, self-generated gas, and magnetic circuit breakers. Among these, vacuum circuit breakers have gained significant popularity due to their efficiency, compact design, and long service life. They are widely used in 10kV substations, where they utilize vacuum as both the insulating and arc-quenching medium. This paper focuses on the analysis and understanding of vacuum circuit breakers.
2. Working Principle, Main Structure, and Characteristics of Vacuum Circuit Breakers
2.1 Working Principle
When the moving and static contacts of a vacuum circuit breaker are separated by the operating mechanism, an electric arc forms between them. Under high temperature, the contact surfaces produce vapor, and if a magnetic field is present, the arc moves rapidly along the tangent direction of the contact surface. Some of the metal vapor condenses on the shield, and once the current reaches zero, the arc is extinguished, allowing the dielectric strength between the contacts to recover quickly.
2.2 Main Components
The vacuum circuit breaker consists of three main parts: the vacuum interrupter, the operating mechanism, and the insulating support base.
2.2.1 Vacuum Interrupter
The vacuum interrupter is the core component, consisting of a sealed insulating cylinder, conductive parts, and a shielding system. It is typically made from ceramic, glass, or glass-ceramic materials and includes a stainless steel bellows for sealing. The conductive system includes fixed and moving contacts, while the shielding system prevents arc products from damaging the insulation and helps improve the electric field distribution.
2.2.2 Operating Mechanism
Common operating mechanisms include spring-operated, electromagnetic, and energy-stored mechanisms. These mechanisms control the movement of the contacts and ensure reliable operation under different conditions.
2.2.3 Additional Components
Other essential parts include the base, insulators, and supporting structures, which ensure mechanical stability and electrical insulation.
2.3 Key Features
Vacuum circuit breakers offer several advantages, including a small contact gap (around 10mm for 10kV models), short arcing time (typically half a cycle), rapid dielectric recovery, long electrical life, compact size, and suitability for capacitive loads. These features make them ideal for use in modern power systems. Popular models include ZN12-10, ZN28A-10, VS1, and ZN30.
3. Common Faults and Troubleshooting
While vacuum circuit breakers are highly reliable, they are not immune to faults. Common issues include reduced vacuum levels, electrical wear on contacts, and mechanical failures in the operating mechanism. For example, a drop in vacuum level may indicate leakage or gas release from internal materials. To detect this, methods like spark meter testing, observing arc color, and using vacuum degree testers are commonly employed. Electrical wear can reduce contact thickness and increase resistance, requiring replacement if the wear exceeds specified limits. Mechanical problems, such as misalignment or poor contact in the trip or closing circuits, can lead to failure to operate. Troubleshooting involves checking the electrical and mechanical systems, adjusting components, and replacing damaged parts when necessary.
4. Conclusion
This paper has analyzed the working principles, structure, and characteristics of vacuum circuit breakers, emphasizing their advantages in terms of performance, reliability, and ease of maintenance. Their widespread use in 10kV power systems highlights their importance in ensuring stable and safe electricity supply. However, it is essential for maintenance personnel to understand the potential faults and proper handling procedures to maintain system integrity and prevent accidents. With continued advancements in technology, vacuum circuit breakers will continue to play a vital role in modern power networks.
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