How do vacuum circuit breakers differ from other types of circuit breakers?

The core difference between vacuum circuit breakers and other types lies in their use of a vacuum as the insulating and arc-extinguishing medium, whereas other breakers utilize substances such as SF6 gas or air. This fundamental distinction leads to significant differences in operating principles, performance characteristics, application areas, and maintenance requirements.

Compared to other types of circuit breakers, the main distinctions of vacuum circuit breakers are evident in the following areas:

• Operating Medium and Environmental Impact

Vacuum Circuit Breakers: Utilize a high vacuum as the medium; containing no internal gas, they pose no risk of gas leakage and cause no environmental pollution. Their environmental performance is superior to that of SF6 circuit breakers.

SF6 Circuit Breakers: Utilize sulfur hexafluoride (SF6) gas as the medium. SF6 is a potent greenhouse gas with a global warming potential 23,900 times that of carbon dioxide; it has a significant environmental impact and requires strict regulation.

• Voltage Rating and Breaking Capacity

Vacuum Circuit Breakers: Primarily used in medium-voltage systems, typically with voltage ratings of 126 kV and below.

SF6 Circuit Breakers: Suitable for higher-voltage systems (exceeding 550 kV) and generally offer higher breaking capacities, reaching up to 63 kA.

• Price and Maintenance

Vacuum Circuit Breakers: Relatively low cost; they require virtually no maintenance over their service life, resulting in low maintenance costs.

SF6 Circuit Breakers: Higher equipment cost; while they have long service intervals, they require regular monitoring of gas pressure, making routine maintenance relatively complex.

• Arc-Extinguishing Principle

Vacuum Circuit Breakers: In a vacuum environment, the near-absence of ionizable gas molecules allows the arc to extinguish rapidly after formation; they possess strong arc-extinguishing capabilities and short arcing times (generally not exceeding 20 ms).

Air Circuit Breakers: Extinguish the arc by utilizing the flow of compressed air or gas; their arc-extinguishing principle differs from that of vacuum breakers.

• Structure and Safety

Vacuum Circuit Breaker: Compact and lightweight; since it uses neither oil nor flammable/explosive gases, there is no risk of fire or explosion.

Air Circuit Breaker: Typically bulky and heavy; requires a large volume of gas to maintain operational status.

Advantages and Disadvantages of Vacuum Circuit Breakers

• Key Advantages

Long service life and high reliability: Minimal contact wear and long mechanical and electrical lifespans make them suitable for frequent operation.

Low maintenance requirements: The sealed structure is unaffected by the external environment; they require virtually no overhaul during their service life (up to 20 years), resulting in minimal maintenance work.

Rapid response: Short arc-extinguishing time allows for the quick interruption of fault currents, preventing the fault from escalating.

• Key Disadvantages

Susceptibility to switching overvoltage: Interrupting low currents can generate current-chopping overvoltage or high-frequency reignition overvoltage.

Performance affected by electric field uniformity: Electrical performance is highly sensitive to the uniformity of the electric field.

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