Working Principle of Vacuum Circuit Breaker

Overview

A vacuum circuit breaker (VCB) is a type of circuit breaker that uses a vacuum as the arc extinguishing medium. It is primarily used in power systems to interrupt or connect load currents and to cut off short-circuit currents during faults. Due to its strong arc extinguishing capability, compact size, and long service life, it is widely used in medium and high voltage power systems.

Working Principle

1. Vacuum Interrupter: The core component of a VCB is the vacuum interrupter, which is a sealed chamber with a high vacuum environment (below 10^-4 Pa). The high insulation strength and arc extinguishing capability of the vacuum allow it to quickly extinguish the arc when the current is interrupted.
2. Contact System: The contact system consists of a moving contact and a fixed contact, usually made of copper alloy and coated with arc-resistant materials.
3. Operating Mechanism: The operating mechanism drives the opening and closing of the contacts through spring, electromagnetic, or hydraulic systems.

Key Features

High Insulation Strength: The high insulation property of the vacuum allows it to withstand high voltages with small contact gaps.

Rapid Arc Extinction: The arc in the vacuum is extinguished quickly at current zero, resulting in a short arcing time.

Long Service Life: The vacuum interrupter is well-sealed, and the contact wear is minimal, leading to a long mechanical life.

Low Maintenance: The simple structure requires minimal maintenance.

Environmentally Friendly: It is oil-free and does not use SF6 gas, making it environmentally friendly.

Application Areas

Power Systems: Used in substations and distribution systems for the protection and control of electrical equipment.

Industrial Applications: Used for the protection and control of large motors, transformers, and other equipment.

Rail Transit: Used in the power systems of electric locomotives and subways for protection.

Selection and Maintenance

Selection: Choose the appropriate model based on parameters such as rated voltage, current, and short-circuit breaking capacity.

Maintenance: Regularly inspect contact wear, the flexibility of the operating mechanism, and the vacuum level of the Vacuum interrupter.

Common Faults and Handling

Contact Wear: Regularly check and replace severely worn contacts.

Operating Mechanism Failure: Inspect the spring, electromagnetic, or hydraulic mechanisms and repair or replace them as needed.

Vacuum Level Drop: Measure the vacuum level with a vacuum tester and replace the interrupter if necessary.

Development Trends

Intelligentization：Integrate sensors and communication modules for remote monitoring and fault diagnosis.

High Voltage Levels: Develop vacuum circuit breakers for higher voltage levels to meet the needs of ultra-high voltage grids.

Eco-friendly Materials: Further reduce environmental impact by using more eco-friendly materials and processes.

Summary

The main functions of a vacuum circuit breaker include:

1. Controlling the connection and disconnection of load currents during normal operation.
2. Quickly interrupting short--circuit currents during faults to protect electrical equipment.
3. Utilizing vacuum arc-extinguishing technology to rapidly extinguish arcs and ensure safe circuit interruption.
4. Enhancing the stability and reliability of power systems.
5. Being environmentally friendly and energy-efficient, suitable for various applications.

Vacuum circuit breakers, with their excellent performance and reliability, play a crucial role in power systems. With technological advancements, their application scope will continue to expand, and their performance will further improve.