# At what cold ambient air temperature will power lines fail?

I'm wondering just how cold it would have to be before electric power can no longer flow through overhead power lines. I know power lines generate a certain amount of heat just as a side effect from electric current, but I don't know if sucking off this heat will make them fail, or if very cold air will make them fail for some other reason. I'm looking for the reason and the approximate air temperature where failure will occur.

There are also transformers and metal pylons to worry about. Presumably wooden telephone poles would be fine, but the big metal pylons in long-distance lines might suffer too much thermal contraction.

I'm interested in overhead power lines only, which are exposed directly to air. Transformers and the metal pylons count too. I'm not interested in underground lines. I'm not interested in power plants themselves, which of course have their own vulnerabilities. Just the transmission infrastructure.

Also, I'm not interested in stormy weather either. I don't care about snow or ice accumulating on the cables, or rain short-circuiting something or wind blowing something down. All I care about is the cold ambient air affecting power transmission.

So how cold does it have to be before overhead power lines fail?

EDIT: For all I know there is no lower limit. Very low temperatures might actually be a benefit if they safeguard against overheating.

• @EnergyNumbers I read your link and still don't know the definition of an XY problem. I have no attempted solution from an engineering-calculation standpoint because I have no idea how to calculate electromagnetic things. I'm asking because I genuinely want to know how cold is too cold for power lines? That would be useful info for many reasons, e.g., to set boundaries on how far north (or south) a small city could be placed. – DrZ214 Nov 24 '15 at 8:16
• @EnergyNumbers That was just a practical/hypothetical example of a useful derivation from the OP. I have this sinking feeling that you've just entrapped me into an XY problem by getting me to ask something different. The motivation for my asking is curiosity. I really hope you're not gonna tell me that is a problem or requires further justification. If further clarification of the OP is needed, then ask me what is not clear. If you want me to restate the same problem in some other language, I can take a crack at it: What is the minimum temperature at which overhead power lines will not work? – DrZ214 Nov 24 '15 at 8:42
• @EnergyNumbers Tell me what it depends on and I'll see if I can specify. Also note in the OP, I specifically mentioned to ignore ice/snow because I know those quickly induce failure and I'm solely interested in ambient air temperature as a limit. As it stands now, I don't see how the question is not a specific engineering problem. Temperature limits are a very real and physical problem that systems had better be designed with in mind. Also note I have no idea if there even is a limit. For all I know, low temperatures are actually a benefit because they safeguard against overheating. – DrZ214 Nov 24 '15 at 9:14