How is the SCCR of any section of a switchboard determined?

The Short-Circuit Current Rating (SCCR) of any section of a switchboard is determined by the lowest Overcurrent Protective Device (OCPD) interrupting rating installed in that section. The SCCR indicates the maximum prospective short-circuit current that the equipment can withstand without damage or creating a hazard.

When a fault occurs in an electrical system, such as a short circuit, the current can increase significantly, potentially damaging equipment or posing safety risks. The OCPD, such as fuses or circuit breakers, is designed to interrupt this current flow when it exceeds a certain level. Therefore, the interrupting rating of the OCPD is critical, as it represents the maximum fault current that the device can safely interrupt. If the SCCR is rated higher than the interrupting capacity of the installed OCPD, there is a risk that the device will not function properly in the event of a fault, leading to unsafe conditions.

Thus, determining the SCCR involves assessing the installed OCPD's lowest interrupting rating, as this rating acts as a limiting factor that defines how much fault current the switchboard can safely handle without risk of failure or unsafe operation.