Vuotovirta

Vuotovirta, or leakage current, is the unwanted electric current that flows outside the intended circuit paths in electrical equipment and installations. It typically originates from imperfect insulation, moisture or contamination, aging of components, or from parasitic paths such as capacitive coupling in EMI filters. Leakage current can travel to chassis, exposed metal parts, or to earth, and may occur during operation or in standby.

Causes and pathways include degraded insulation on cables and components, condensation or damp surfaces, dust or chemical contamination, damaged seals, and the presence of capacitors used for noise suppression. In devices with EMI filters or switch-mode power supplies, small currents can flow through safety capacitors to earth, contributing to the overall leakage current.

Safety and operation considerations are central to vuotovirta. Excessive leakage current increases the risk of electric shock to users and can cause nuisance tripping of residual current devices (RCDs), which are designed to protect people from such leakage. It can also affect the accuracy of sensitive measuring equipment and contribute to electromagnetic interference.

Measurement and mitigation involve testing insulation resistance and leakage paths, using leakage current meters or insulation testers. Design approaches to reduce leakage include proper insulation, effective enclosure and grounding, double insulation in Class II devices, careful layout to minimize parasitic paths, and judicious use of EMI filters. Standards such as IEC 60364 and IEC 60335-1 govern limits and testing practices to ensure electrical safety and functional reliability.