Jordfelsfunktioner

Jordfelsfunktioner refer to protective measures in electrical systems designed to detect leakage of current to earth (ground) and to disconnect power to prevent electric shock and reduce fire risk. They are implemented in devices such as residual current devices (RCDs or GFCIs), residual current circuit breakers with overcurrent protection (RCBOs), and industrial earth-fault protection relays. Their common principle is to monitor the balance between current in live conductors and the return conductor; any residual current indicates leakage to earth and triggers a rapid interruption of the circuit.

Typical thresholds vary by application. In domestic and general installations, protection thresholds around 30 mA are common; in more sensitive settings or equipment protection, 100–300 mA may be used. In North American GFCIs used for personnel protection, thresholds can be as low as 4–6 mA. Trip times are designed to be fast, often within milliseconds to tens of milliseconds.

Jordfelsfunktioner are widely used in residential buildings, commercial and industrial facilities, and machinery. They enhance safety for people who might touch exposed conductors and help prevent electrical fires caused by insulation faults. In industrial settings, earth-fault protection is often integrated with motor protection and control relays to detect faults in transformers, motors, and feeders.

Standards and guidance: design and implementation follow electrical installation standards such as the IEC 60364 family and the IEC 61008/61009 series around residual-current devices. Local codes, such as the NEC in the United States, provide requirements for GFCI installations in wet locations and specific equipment applications.