IEC 60186:1969

Applies to new voltage transformers for use with electrical measuring instruments and electrical protective devices at frequencies from 15 Hz to 100 Hz.
The general requirements apply to all voltage transformers, but, for certain types, e.g. capacitor voltage transformers, the requirements are subject to the modifications stated in the appropriate chapter. Although the requirements relate basically to transformers with separate windings, they are also applicable, where appropriate, to autotransformers. The standard does not apply to transformers for use in laboratories.