scope:

This part of IEC 62505 is applicable to single-pole and two-pole alternating current (a.c.) circuit-breakers which are:

• designed for indoor or outdoor fixed installations in tractions systems, and

• operated with an a.c. line voltage and frequency as specified in IEC 60850:2014.

NOTE 1 IEC 60850 specifies the a.c. 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.

NOTE 2 As rails of a.c. traction systems are typically connected to earth and included in the return current path all phase to earth voltages will be within the tolerances as specified in IEC 60850. Nevertheless phase to phase voltages are sometimes higher, e.g. in autotransformer systems.

This Standard is also applicable to the operating devices of circuit-breakers and to their auxiliary equipment.

This Standard does not address circuit-breakers with dependent manual operating mechanism.

NOTE 3 It is impossible to specify a short-circuit making current for these circuit-breakers and it is likely that such dependent manual operation is not meeting safety considerations.