scope:

This part of IEC 62505 is applicable to new current transformers which are:

- intended for use in indoor or outdoor fixed installations in traction systems, and

- operated with an AC line voltage and frequency as specified in IEC 60850.

NOTE 1 IEC 60850 specifies the AC traction systems:

15 kV 16,7 Hz,

12 kV 25 Hz,

12,5 kV, 20 kV also 25 kV with 50 Hz and

12,5 kV, 20 kV, 25 kV also 50 kV with 60 Hz z.

NOTE 2 As rails of AC traction systems are typically connected to earth and included in the return current path, all phase to earth voltages are subject to the limits as given in IEC 60850. Nevertheless, conductor to conductor voltages are some times higher, e.g. in autotransformer systems.

This document does not provide specific requirements for AC traction systems supplied with a frequency of 25 Hz or with a nominal voltage of 12,5 kV or 50 kV. Nevertheless requirements set out in this document can also be used as a guidance for these systems.

This document also applies to low-voltage current transformers which are operated in a traction system with an AC line voltage and frequency as specified in IEC 60850.

NOTE 3 These are e.g. current transformers without primary conductor and primary insulation of their own, e.g. of the cable or ring core type.

Current transformers are mainly used with:

- measuring instruments,

- protective devices.

This document also applies to current transformers other than inductive types as far as reasonably possible. Requirements of this document have priority.

NOTE 4 Combined current and voltage transformers are typically not used in fixed installations in traction systems.