Does your circuit breaker really protect you?

Breaking capacity is a fundamental element in the protection of electrical installations. It defines the ability of a device to interrupt a short-circuit current without sustaining damage. For example, a standard household circuit breaker typically has a breaking capacity of 3 kA to 6 kA, while in industrial settings, this value can reach 50 kA or even 100 kA for high-voltage networks. Insufficient breaking capacity can lead to destructive electrical arcs, endangering equipment and personal safety. Compliance with standards such as IEC 60947 for industrial circuit breakers ensures effective protection against overcurrents. Consequently, choosing the right breaking capacity is essential for ensuring the reliability and safety of electrical systems, reducing the risk of failures and fires.

Definition and Importance

Breaking capacity represents the maximum current that a circuit breaker or fuse can safely interrupt. It prevents short circuits from causing overheating, electrical arcs, and equipment damage. An undersized circuit breaker may fail to interrupt the fault current, increasing the risk of fire or network damage. Additionally, breaking capacity depends on voltage and current type (AC or DC), influencing technical choices. Adhering to thresholds defined by standards such as IEC 60947 or NF C 63-120 ensures optimal protection against electrical incidents.

Typical Breaking Capacity Values

Standard breaking capacity values vary depending on the usage environment:

Installation Type	Typical Breaking Capacity
Residential	3 kA – 6 kA
Light Industrial	10 kA – 15 kA
Heavy Industrial	20 kA – 100 kA

Comparison Between Circuit Breakers and Fuses

Circuit breakers and fuses are the primary breaking devices in electrical systems. Here is a comparative table:

Criterion	Circuit Breaker	Fuse
Reusability	Yes	No
Response Time	Fast	Very fast
Cost	Higher	Lower
Breaking Capacity	High	Variable depending on type

How to Choose the Right Device?

Choosing between a circuit breaker and a fuse depends on several technical and economic criteria.

• Estimated short-circuit current: It is crucial to select a device with a breaking capacity exceeding the maximum possible current. For example, in a household panel, a 6 kA circuit breaker is usually sufficient, whereas an industrial installation exposed to high short-circuit currents, such as a metallurgical plant, requires circuit breakers rated at 50 kA or more.
• Type of installation: A residential home uses miniature circuit breakers rated between 3 kA and 6 kA, while a steel plant or refinery requires much more robust protection.
• Cost and maintenance: Fuses, such as HPC models used for motor protection, are affordable but must be replaced after each fault. In contrast, a thermal-magnetic circuit breaker, although more expensive, can be reset and is more practical for installations requiring frequent intervention.

Conclusion

Breaking capacity is a critical factor in the protection of electrical installations. A well-chosen circuit breaker or fuse ensures safety and reliability.