Providing certain definitions of terms used in the EU Taxonomy helps get a better grasp of the nature of the requirements.

In its Regulation 548/2014, the EU defines the term 'medium power transformers'.

It understands medium power transformers as power transformers with a highest voltage for equipment higher than 1,1 kV, but not exceeding 36 kV and a rated power equal to or higher than 5 kVA but lower than 40 MVA.

It further defines ‘highest voltage for equipment’ (Um) applicable to a transformer winding as the highest r.m.s phase-to-phase voltage in a three-phase system for which a transformer winding is designed in respect of its insulation.