Instrument transformers - Part 1: Current transformers
Executive summaryRequirements for current transformers used in electrical measuring instruments and protective devices.
AbstractThis part of IEC 60044 applies to newly manufactured current transformers for use with electrical measuring instruments and electrical protective devices at frequencies from 15-100 Hz. Although the requirements relate to transformers with separate windings, they are also applicable to autotransformers.
Clause 11 of this European Standard covers the requirements and tests that are necessary for current transformers for use with electrical measuring instruments.
Clause 12 covers the requirements and tests that are necessary for current transformers for use with electrical protective relays, and in particular for 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 are given in Clause 13 for class PR transformers and in Clause 14 for class PX transformers.
Clause 13 covers the requirements and tests that are necessary for current transformers for use with electrical protective relays, and in particular for absence of remanent flux.
Clause 14 covers the requirements and tests that are necessary for current transformers for use with electrical protective relays, and for forms of protection for which knowledge of the transformer’s secondary excitation characteristic, secondary winding resistance, secondary burden resistance and turns ratio is sufficient to assess its performance in relation to the protective relay system with which it is to be used.
History and related standardsThis European Standard supersedes BS 7626:1993 which is withdrawn.
This Standard includes the following cross-references:
IEC 60028:1925, IEC 60038:1983, IEC 60044-6:1992, IEC 60050(321):1986, IEC 60060-1:1989, IEC 60071-1:1993, IEC 60085:1984, IEC 60121:1960, IEC 60270:1981, IEC 60567:1992, IEC 60599:1978, IEC 60721, IEC 60815:1986 and CISPR 18-2:1986.
