electrical conductor sag practical guide


For conductor sag, is there a practical guide? Is there a rule of the thumb method that says for a span of 'x' meters - to calculate the conductor length, add 10% to the span length. Meaning, conductor length = span length + 10% span length. Is there a rule of thumb that says something like that? I have been through the calculation process and on paper it looks very impressive. But what about on the field, say, when there are no proper equipments etc.

Thanks, LS

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They look it up using tables or charts. For small distribution lines, the crews just tension the lines to some standard value, possibly corrected for extremes in ambient temperature. Well written construction standards obviate the need to do a calculation for every small job.

Two important reasons one must 'calculate' sag is 1) to ensure that under extreme cold temperatures, conductor shrinkage doesn't place unacceptable stresses on structures and 2) at high ambient/high I^2R temperatures conductors don't sag down and violate clearance rules from underbuild, structures, right-of-ways, etc.

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Paul Hovnanian P.E.

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