IEC 60076-15:2015 applies to three-phase and single-phase gas-filled power transformers (including auto-transformers) with the exception of certain categories of small and special transformers such as: - single-phase transformers with rated power less than 1 kVA and three-phase transformers less than 5 kVA; - transformers, which have no windings with rated voltage higher than 1 000 V; - instrument transformers; - traction transformers mounted on rolling stock; - starting transformers; - testing transformers; - welding transformers. This second edition of IEC 60076-15 cancels and replaces the first edition published in 2008 and constitutes a technical revision. The following main technical changes from the first edition are: - Modified in accordance with the related revised standards of IEC 60076-1, IEC 60076-2, IEC 60076-3 and related items of SF6 gas in the revised standard of "High-voltage switchgear and controlgear; - Added the clause "minimum power under alternative cooling modes"; - Added the clause "safety, environmental and other requirements"; - Added the clause "d.c. currents in neutral circuits"; - Added the clause "electromagnetic compatibility (EMC)"; - Added the clause "high frequency switching transients".