E VDE-AR-N 4226 Anwendungsregel:2026-02

This application guideline defines the conditions under which equipment in bays and transformers in high- and extra-high-voltage networks (> AC 52?kV) can be operated at increased current ratings. Rated currents are specified for standardized reference conditions (e. g. 40?°C ambient temperature). Under more favorable weather conditions, such as lower ambient temperatures, higher operating currents can be applied without exceeding permissible material temperatures or impairing equipment functionality. Furthermore, the inherent thermal capacity of equipment allows temporary loading significantly above rated current without surpassing thermal limits. The guideline outlines the organizational and technical measures required to enable such increased equipment utilization and provides illustrative application examples, particularly for circuit breakers, disconnectors, busbars, and transformers.