4 ms·

Anyone know why the power cables in the image zig zag up and down? Seems like it would require more cable than a straight line so I am guessing there is a reas

Anyone know why the power cables in the image zig zag up and down? Seems like it would require more cable than a straight line so I am guessing there is a reason for it

dmoy 10mo ago
https://news.ycombinator.com/item?id=46334725 https://news.ycombinator.com/item?id=46334725 TL;DR Camera makes it look more than it is, it's mostly just sag If you want to see electrical with significant zig zag, open up the wall of a house that was built without very detailed plans, but still hired an electrician with a lot of prior experience being told to move stuff after the fact. They just zig zag it like crazy under the drywall, so there's an incredible amount of slack to pull wire to new and exciting unplanned locations.
- blackhaj7 10mo ago
  Very interesting, thanks!
7952 10mo ago
My guess is that the droop is just due to gravity. And it is easier to affix in fewer places. But the style of photography exaggerates the effect.
sokka_h2otribe 10mo ago
Some good reasons: -gotta hang them somehow, and in a very controlled way. -thermal expansion, very important not to cause axial strain on a cable, which happens on tight bends. You might think it would be enough to just have slack "somewhere" but I think you get to have many many micro adjustments when you have it across the entire length. Why don't HV telephone lines do this? I have no idea. Maybe because they can hang and droop more easily. I hope someone more knowledgeable gives a real answer.
- matt-p 10mo ago
  You are basically spot on. Thermal expansion (primarily) but you need it to be evenly spread for lots of boring reasons like as you mentioned axial force reduction, fatigue life, anchor load limits and so on. These tunnels just use forced air to cool the (XPLE) cables so they're not oil filled or anything. Tunnels are basically all thermally constrained.
  - blackhaj7 10mo ago
    Interesting, thanks!
- blackhaj7 10mo ago
  Thanks for the explanation!

Anyone know why the power cables in the image zig zag up and down? Seems like it would require more cable than a straight line so I am guessing there is a reason for it

dmoy 10mo ago

https://news.ycombinator.com/item?id=46334725 https://news.ycombinator.com/item?id=46334725 TL;DR Camera makes it look more than it is, it's mostly just sag If you want to see electrical with significant zig zag, open up the wall of a house that was built without very detailed plans, but still hired an electrician with a lot of prior experience being told to move stuff after the fact. They just zig zag it like crazy under the drywall, so there's an incredible amount of slack to pull wire to new and exciting unplanned locations.

blackhaj7 10mo ago
Very interesting, thanks!

7952 10mo ago

My guess is that the droop is just due to gravity. And it is easier to affix in fewer places. But the style of photography exaggerates the effect.

sokka_h2otribe 10mo ago

Some good reasons: -gotta hang them somehow, and in a very controlled way. -thermal expansion, very important not to cause axial strain on a cable, which happens on tight bends. You might think it would be enough to just have slack "somewhere" but I think you get to have many many micro adjustments when you have it across the entire length. Why don't HV telephone lines do this? I have no idea. Maybe because they can hang and droop more easily. I hope someone more knowledgeable gives a real answer.

matt-p 10mo ago
You are basically spot on. Thermal expansion (primarily) but you need it to be evenly spread for lots of boring reasons like as you mentioned axial force reduction, fatigue life, anchor load limits and so on. These tunnels just use forced air to cool the (XPLE) cables so they're not oil filled or anything. Tunnels are basically all thermally constrained.
- blackhaj7 10mo ago
  Interesting, thanks!
blackhaj7 10mo ago
Thanks for the explanation!