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What is the short-circuit breaking capacity of the distribution box?

Release time： 2025-09-30

The short-circuit breaking capacity of a distribution box refers to the ability of its internal circuit breaker or fuse to quickly disconnect the circuit in the event of a short circuit, thereby protecting equipment and ensuring personal safety. Here’s some relevant information about the short-circuit breaking capacity of distribution boxes:

Classification of Short-Circuit Breaking Capacity

Rated Ultimate Short-Circuit Breaking Capacity (Icu) "This is the maximum current value that the circuit breaker can interrupt without sustaining damage."
Rated Short-Circuit Breaking Capacity (Ics) "This is the value of the short-circuit current that the circuit breaker can interrupt under normal operating conditions."

Levels of short-circuit breaking capacity

Standard Type (S-Type) : Suitable for general low-voltage distribution equipment, with a typical breaking capacity of around 6 kA.
High-Capacity (H-Type) : Suitable for equipment with high short-circuit breaking capacity requirements, featuring a breaking capacity of 10 kA or higher.
Ultra-High Breaking Capacity (L-Type) : Suitable for special applications, with higher breaking capacity—up to 50 kA.

Criteria for selecting short-circuit breaking capacity

Short-circuit current level : It needs to be determined based on the grid's power supply capacity and the level of grid short-circuit current.
Device type and rated current : Different types of equipment have varying requirements for the breaking capacity of circuit breakers, and the rated current of the equipment also influences the selection of the circuit breaker.

Common Standards for the Short-Circuit Breaking Capacity of Distribution Boxes

Low-Voltage Distribution Box : Generally, the short-circuit breaking capacity of the circuit breaker should be no less than 6 kA.
Special Environment Distribution Box For outdoor or explosion-proof distribution boxes, the short-circuit breaking capacity of their circuit breakers may need to be higher to meet the requirements of special environments.

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