Leckströme

Leckströme, or leakage currents, are unintended electric currents that flow through insulation, along surfaces, or through imperfect conductive paths in electrical equipment. They differ from the designed current paths and from fault currents, and they are often small but not negligible for insulation performance and safety.

Leakage currents can occur through several mechanisms. Bulk dielectric conduction happens when charge carriers move through the insulating material itself. Surface leakage follows contaminated or moist surfaces, especially in high-humidity environments, while localized defects, moisture ingress, or aging can create conductive paths that increase leakage. In high-voltage equipment, leakage currents may vary with temperature, voltage, and environmental conditions, and can contribute to heating, insulation degradation, or misleading fault signals.

Measurement and monitoring of leakage current are important for assessing insulation integrity. Insulation resistance tests apply a high DC voltage and measure the resulting current, providing a standard indication of leakage. In some applications, leakage currents are specified or bounded to ensure safe operation and long-term reliability. Typical leakage levels depend on voltage, material, and environment and can range from microamps to milliamps for insulated components.

Mitigation focuses on improving insulation quality and reducing pathways for unintended current. Approaches include selecting low-conductivity materials, ensuring clean and dry surfaces, applying protective coatings, increasing creepage and clearance distances, and controlling humidity and contaminants. In electronic devices, leakage current is also an important parameter for components such as capacitors, diodes, and transistors, influencing efficiency and leakage-related loss.

See also: insulation resistance, dielectric strength, creepage and clearance, partial discharge.