CSA C22.3 No. 5.1:93

Scope 1.1 This Standard outlines the principles and general practices of electrical protection applicable to overhead supply systems operating at more than 750 V but less than 50 kV phase to phase and communication systems, where the lines of those systems are located so that inadvertent electric contact between them could occur, resulting in a contact voltage not exceeding a limit agreed to by the communication and supply companies. 1.2 This Standard applies to overhead supply and communication systems that meet the requirements of CSA Standard CAN/CSA-C22.3 No. 1 where coordinated electrical protecticn is specified. 1.3 The following effects are within the scGpe of other Standards and therefore are excluded from this Standard: (a) the effects on communication conductors entering power stations or passing through the zone of influence of a station's ground potential rise (GPR): (b) the effects of faults other than single phase-to-ground faults: and (c) the effects of longitudinal induction and ground potential rise that result from normal operating or fault conditions.