This part of IEC 44 applies to newly manufactured current transformers for use with electrical measuring instruments
and electrical protective devices at frequencies from 15 Hz
to 100 Hz.
Although the requirements relate basically to transformers with separate windings, they are also applicable, where appropriate, to autotransformers.
Clause 11 covers the requirements and tests, in addition to those in clauses 3 to 10, that are necessary for current transformers for use with electrical measuring instruments.
Clause 12 covers the requirements and tests, in addition to those in clauses 3 to 10, that are necessary for current transformers for use with electrical protective relays, and in particular for forms of protection in which the prime requirement is the maintenance of
accuracy up to several times the rated current.
For certain protective systems, where the current transformer characteristics are dependant on the overall design of the protective equipment (for example high-speed balanced
systems and earth-fault protection in resonant earthed networks), additional requirements may be necessary.
Current transformers intended for both measurement and protection shall comply with all the clauses of this standard.