CSA C22.3 No. 1:20 Overhead systems.
5 Clearances, separations, and spacings 5.1 General Clause 5 specifies clearances, separations, and spacings involving overhead line components, and their relationship to each other, to the ground, and to other plant. The clearances, separations, and spacings specified in Clause 5 are the basic values required for public safety and are not intended to address the minimum approach distance to electrical installations as specified in occupational health and safety regulations. Note: Refer to CAN/CSA-C60071-1 and CAN/CSA-C60071-2 for guidance. 5.2 General application 5.2.1 Construction and day-to-day clearances The clearances specified in Clause 5 for wires and conductors are minimum values related to maximum specified loads and service conditions and represent design limits rather than clearances for construction or day-to-day operation. Clearances under day-to-day conditions are greater than the minimum clearances specified in Clause 5 when loads and service conditions are less severe than specified maximum conditions. Clearances provided at the time of construction shall by design be sufficiently greater than the minimum clearances specified in Clause 5 to ensure that the actual clearances under maximum specified loads and service conditions meet minimum clearance requirements. Note: Clearances specified in the Canadian Electrical Code, Part I, apply at the time ofinstallation rather than under specified maximum conditions and are therefore larger than those specified in the Canadian Electrical Code, Part III, for the reasons given in this Clause. 5.2.2 Vertical design clearances Unless otherwise specified, vertical clearances shall apply under conditions of maximum sag of the wires, conductors, or cables, whether thermally loaded (see Clause 5.2.6) or physically loaded under wind and/or ice (see Clause 7). The calculation of final maximum thermal sag for a wire, conductor, or cable shall be based on its final unloaded ambient air sag condition.
5.2.5 Conductor temperature for thermal loading conditions 220.127.116.11 For wires or conductors carrying currents less than 1/3 of their rated ampacity, the design conductor temperature for the thermal loading condition shall be 50 °C. Note: See the definition ofrated ampacity in Clause 3. 18.104.22.168 For wires or conductors carrying currents greater than 1/3 of, but not exceeding, their rated ampacity, the design conductor temperature for the thermal loading condition shall be a) calculated in accordance with ANSI/IEEE 738 for the anticipated worst-case conditions; or b) 100 °C for bare conductors and 80 °C for covered conductors.CSA C22.3 No. 1 pdf download.