Provides requirements for a satisfactory life of conductors and insulation subjected to the thermal effects of carrying current for prolonged periods of time in normal service. Includes a series of tables containing the relationship between cross-sectional area of conductors and the load depending on type of conductor material, type of insulation and method of installation. Relates only to non-armoured cables and insulated conductors having a nominal voltage not exceeding 1 kV a.c. or 1,5 kV d.c. Does not apply to armoured single-core cables.