The standard basis of rating in this specification is the Continuous Maximum Rating. It applies to single-phase and polyphase transformers (including auto-transformers) for power and lighting having windings insulated with Class A and/or Class B materials, the transformers being rated at 1 kVA or over if single-phase and 5 kVA or over if polyphase. Reactors, earthing transformers and buried transformers, if continuously rated, should comply with this specification where applicable. If they are not continuosly rated the standard temperature-rises do not apply, but in all other respects the apparatus should comply with this specification. In the case of buried transformers, the standard temperature limits for continuous rating apply only in respect of the rating of such transformers when operating in free air above ground, under which conditions the rated kVA would be higher than when buried, depending on the nature and heat conductivity of the soil or surrounding material. This specification does not apply to constant-current power and lighting transformers; instrument transformers; traction transformers mounted on electric locomotives or other vehicles and used for supplying electrical energy for traction; testing transformers; auto-transformer starters or induction regulators.