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ITGlossary · Protection and installation
Circuit Protection
Devices such as fuses and circuit breakers that open the circuit on overcurrent or short circuit to prevent damage.
Technical level:Intermediate
Circuit protection includes miniature circuit breakers, fuses, residual current devices and the internal protections of equipment. Their purpose is to cut the supply quickly when current exceeds safe limits or, in the case of an RCD, when leakage to earth occurs, so that cables do not overheat and no fire, electric shock or equipment damage results.
In a UPS installation, both input and output need attention. The input breaker must withstand the UPS's maximum current, which includes battery charging. On the output, when the UPS runs on battery, the short-circuit current it can deliver is limited, so a large breaker may not trip in time.
Always follow the values in the UPS manual and ensure proper selectivity: in a short circuit, the breaker of the affected line should trip, not the whole installation.
Related terms
- Short CircuitAn unintended low-resistance connection between conductors that causes a sudden, dangerous surge of current.
- IK Rating (Impact Protection)Scale from IK00 to IK10 under IEC 62262 that shows how much impact energy the enclosure of an electrical device can withstand.
- Overcurrent ProtectionA system designed to interrupt excessive current to protect UPS and loads.
- Automatic Voltage Regulator (AVR)A device that automatically maintains a constant voltage level to protect electrical equipment from fluctuations.
- Emergency Power Off (EPO)A safety feature that allows immediate shutdown of power to connected systems in an emergency.
- Ground FaultAn unintended flow of current from a live conductor to earth or to a device’s metal casing.