IEC 60186:1987

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.
The requirements for inductive voltage transformers are superseded
by IEC 60044-2 (1997).