This part of IEC 6021 4 applies to on-load tap-changers of both resistor and reactor types, deenergized tap-changers, and their motor-drive mechanisms.
It applies mainly to tap-changers immersed in mineral insulating oil according to IEC 60296 but may also be used for tap-changers with air or gas insulation or immersed in other insulating liquids insofar as conditions are applicable.
It applies mainly to tap-changers with arcing contacts but may also be used for arcing-free onload tap-changers (such as electronic switching) insofar as conditions are applicable.
This part of IEC 6021 4 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.
