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Comment by cool_dude85 | Hacker News Reader

Strange not to mention wire weight which I gather is an extremely important factor. If these are also heavier, they may sag more for strictly physical reasons and that would cause problems. I guess the modeling behind this article probably takes that into account.

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> "Chojkiewicz and her colleagues at Berkeley’s Energy and Resources Group and Goldman School of Public Policy studied the use of advanced conductors that wrap more aluminum around a smaller, stronger composite core. These Aluminum Conductor Composite Cores (ACCCs) are more conductive and can operate at higher temperatures, resulting in roughly a doubling of capacity for an equivalent diameter wire."

It isn't clear from the text, but the wires might not actually be any heavier, given that they replace the steel core with a composite.

Aluminum is about 2.7 g/cm^3, whereas steel is around 7.85.

I'd imagine they can switch to a slightly smaller cable size if they have to keep to the original weight and a new cable happens to be a little heavier at the same diameter.

I'm kind of surprised they don't lose the advantages of stranded cable when switching to something that looks more like a solid cable. As I understand it, for AC wiring you usually want a lot of strands because most of the current tends to travel on the surface. Maybe that's less of a thing for high voltage. Or maybe the seams between the strands are enough to cause the skin effect even if they're tight-fitting.

Skin effect is a high-frequency thing. From memory the down-rating tables start at 100 kHz.

Skin effect works at all frequencies besides DC. At 60 Hz it’s 8.5mm. So, solid conductors thicker than 17mm have some skin loss. You can mitigate this by winding multi strand wire in a particular way, though.

Increased weight makes reconductoring much more difficult as the structures are designed to carry specific weight. Increased size can also impact structure loading from ice or wind. So, generally, reconductoring does not materially increase weight.

The primary difference between the traditional conductors and advanced conductors is temperature tolerance. Most transmission lines are aluminum conductors with a steel core for strength (ASCR). As current increases, so does temperature, causing lines to sag (or the steel anneal if too hot).

Advanced conductors use a different composition to operate at higher temperatures, or otherwise carry more current (one example: aluminum conductor, composite reinforced, or ACCR) so as to have similar weight (and profile) to the original, traditional conductor.

Anywhere that icing is possible during the winter, the static weight of the conductors is not generally the dominant design constraint; it is the diameter of the cable and the resulting additional load when icing occurs. Weight really only increases sag, which constrains attachment height, but wind gusts with increased wind resistance increase horizontal load. In areas that don't get ice, diameter drives wind loading, again making wind gusts the dominant failure mode for pole lines. This comes about as most poles and/or other support structures for overhead conductors have far greater strength vertically than horizontally.

I've spent far too much time over the last couple of years learning pole line design using QuickPole. The other factor that keeps cropping up in my designs are grading and/or positioning issues. Putting a pole even 50cm out of line with other poles can result in it failing loading due to the added horizontal load on the pole. On a recent design I had to add downguys and anchors to 2 poles because they were out of line, a mistake during installation that nobody paid attention to. The same thing happens when a pole that is too tall is installed in an existing pole line. The wires to adjacent poles add horizontal force to the top of the pole. On one design I had a pole failing because of that, but it was fine if all the conductors were lowered 5 feet.

All I wanted to do was put fibre optic cables on poles to serve my home...

Oh, rabbit holes....

Composite-core cables are lighter. The core is carbon and fiberglas fiber, rather than steel.[1]

[1] https://compow.com/blog/midal-accc

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