This part of IEC 60214 applies to on-load tap-changers of both resistor and reactor types, offcircuit tap-changers, and their motor drive mechanisms. It applies mainly to tap-changers immersed in transformer oil according to IEC 60296 but may also be used for tap-changers with gas insulation or immersed in other insulating liquids insofar as conditions are applicable. It applies to power and distribution transformers of all types and also to reactors. It does not apply to transformers and reactors mounted on railway rolling stock.