Short circuit value of circuit breaker
Release time:
2020-12-07
Circuit breakers protect electrical equipment from damage caused by short-circuit currents. However, the "short circuit current" will vary by application. How do IEC and EN standards help designers properly specify overcurrent protection in electrical equipment?
In any modern society, a continuous supply of electricity is critical. Without electricity, most homes, commercial businesses and factories would be paralyzed. This power must be delivered safely and reliably to end users, and distribution switchgear plays a major role. Because of the obvious hazards involved, such switchgear or local distribution boards must be designed to protect the equipment from a fault by cutting off the faulty circuit while ensuring that the unaffected circuit continues to operate. Short circuits can place significant stress on equipment, so when designing switchgear assemblies or switchboards, thermal and dynamic stresses caused by maximum short-circuit currents at field connection points must be considered. To prevent damage to equipment (or personnel), use a short-circuit protection device to cut off short-circuit current at the connection point.
More commonly used for this switching task are Molded Case Circuit Breakers (MCCB), Miniature Circuit Breakers (MCB), Residual Current Operated Circuit Breakers (RCCB) and Residual Current Operated Circuit Breakers with Overcurrent Protection (RCBO). These devices are marked with a maximum short-circuit capacity to enable panel manufacturers to select the correct product for the application. This type of circuit breaker is suitable for isolation, but an isolating switch is usually also installed so that the equipment is completely de-energized for service or maintenance.
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