Canadian Electric Code - Underground Installation

I will reply to this later this evening.

Thanks North of 60, I am not the originator of the question but I am looking for your reply as this is a good question.

Also do you have any input

1) to run two 3 phase circuits (15kv, 3c, #2, teck and 1kv, 3c, 350mcm in the same conduit), as the code calls for a barrier. I know I can not run two different voltages in one conduit if the lower voltage circuit cable has to be rated to the same voltage as the higher one. But I do not know it both are teck cables this rule is still valid.

2) On the cable tray there is existing 15kv URD cable, and I want to run a new 3c-teck cable, does the teck armored be considerd as a mechanical separation running with URD. I know if both circuit are armored, yes the armor is enough physical separation, but if one circuit is URD and one is teck, is still enough mechanical separation?

Tables 1, 2, 3 & 4 of the CEC, used to determine ampacity ratings for conductors, do not take into consideration any factors other then temperature.

When we are talking about direct buried cables, there are many other factors that are implicated in determining ampacity ratings. Such additional factor include, length and profile of the burial of the cables, depth of burial (which is different then the requirements found in 12-012 by the way), the spacing between cables, the thermal resistivity of the soils used, the maximum ground temperatures encountered (if over 20 deg C) at burial depth and the proximity of other current carrying cables.

So... CEC rules 4-004(1)(d), for copper conductors, and 4-004(2)(d), for aluminum conductors, mandates the use of the method identified in IEEE 835 for determining ampacity of and the cable layout to be used for underground single, two, three and four conductor cables when direct buried.

The IEEE 835 methodology also factors in inductive reactance and the un-equal sharing of currents that can result from cables effecting each other in this way.

For cables assemblied with more then 4 conductors, use the values arrived at via the IEEE 835 method and apply the derating factors in table 5C.

Appendix B & D of the CEC in the sections you mentioned have many tables and diagrams that help in determining the proper procedures.

Contact the AHJ in your jurisdiction and he, or she, will tell you what is required to use the IEEE 835 tables.

The information shown in rule 12-108 is meant for cable in free air or in tray.

Thank you, very professional thorough reply. Could you have any reply to the second gust additional question, that is a good question as well.

It should be noted that the CEC rules, 4-004(1)(d) and 4-004(2)(d), that mandate IEEE 825 be used for direct buried conductors has been expanded so that it now reads... "direct buried or in a raceway".