Vikavirtoja

Vikavirtoja, or fault currents, are abnormal electrical currents that flow in power systems when a fault occurs, such as a short circuit or a grounding fault. They are typically several times larger than normal operating currents and are central to the design, protection, and safety of electrical networks.

Common fault types include three-phase faults, single-line-to-ground faults, line-to-line faults, and double-line-to-ground faults. Among these, three-phase faults generally produce the largest currents, while single-line-to-ground faults are the most frequent in many networks. Fault currents are inherently unbalanced in the case of non-three-phase faults, requiring specialized analysis.

Causes of fault currents range from insulation breakdown and equipment failure to external factors like weather, contact with conductors, or unintended connections. The resulting currents can cause equipment damage, overheating, voltage dips, and premature operation of protective devices if not properly managed.

Analysis of fault currents uses network impedance models, and for unbalanced faults the method of symmetrical components. The peak or rms fault current is determined by source impedance, network topology, and generation during the fault. Engineers use per-unit systems and short-circuit calculations to estimate values for protection settings and equipment ratings.

Protection and safety rely on protective relays, circuit breakers, fuses, and appropriate clearance practices to interrupt fault currents quickly, limiting damage. Standards and guidelines for calculating and coordinating fault currents are provided by bodies such as IEC (for example IEC 60909) and IEEE/NFPA in various regions. Accurate estimation supports reliable operation, safe maintenance, and the proper selection of transformers, cables, and switchgear.