feilkurrents

Feilkurrents, or fault currents, are abnormal currents that flow in an electrical power system when insulation fails or a fault path is created. They occur during short-circuits, earth faults, or line-to-ground faults, and can have magnitudes many times the normal operating current. The magnitude depends on system impedance, source voltage, and the location of the fault. In AC systems, fault currents rise quickly and have a high initial peak followed by a decaying transient; DC systems show different transient behavior.

Fault currents pose risks to equipment, insulation, and personnel, causing overheating, damage, arcing, and triggering protective devices. Detecting and interrupting fault currents quickly is essential to minimize damage and maintain safety.

Protection schemes use overcurrent protection, such as fuses and circuit breakers, and specialized devices for ground faults, residual current devices (RCDs/earth-leakage), and arc-fault circuit interrupters. Protective relays coordinate with devices to isolate faults while keeping service to non-faulted portions.

Calculations of prospective fault current are part of system design, using source impedance, transformer impedances, and network topology. In utility practices, fault studies estimate maximum prospective fault current at substations to select appropriately rated devices. Standards from organizations such as IEC and ANSI provide methods for calculating, testing, and specifying protection against fault currents.

Mitigation includes proper insulation, clearances, proper conductor sizing, grounding practices, and regular maintenance. In industrial and electrical engineering contexts, understanding fault currents is essential for safety analysis, reliability, and compliance with electrical codes.