4 ms·

> With proper engineering This tower looks weird. Overhead three-phase transmission is super common in the EU and I've never seen anything like this "transpos

> With proper engineering This tower looks weird. Overhead three-phase transmission is super common in the EU and I've never seen anything like this "transposition tower" that swaps the wires around in the air and I don't really see why it would make much sense to do so mid-line. Wouldn't it be easier to swap the wires around at the start or end of a line, or inside a substation? Also, as far as I can tell (from sometimes photographing these things with telephotos), the insulators seem to generally be bolted to the mast instead of being hooked in, so this entire failure mode of hooks wearing out (or dislodging?) doesn't exist. (Okay, now you have to worry about changing loads on bolts, fair enough).

petertodd 6y ago
Swapping the wires around at the start or end of the line doesn't swap them frequently enough. It's actually quite like a twisted pair in an ethernet cable: you swap the order frequently to average out the different position-dependent electrical characteristics to get a uniform characteristic. The EU probably does that less frequently simply due to higher density, and thus fewer long stretches of transmission line. I've personally seen a transposition tower in the EU on a line running across a mountain, so they do exist. https://en.wikipedia.org/wiki/Transposition_tower https://en.wikipedia.org/wiki/Transposition_tower
- formerly_proven 6y ago
  TIL. Germans of course have their Verdrillschemata to place Verdrillmasten properly, but it seems they're quite rare. There's a Wikipedia article with an example transmission line, but it notes that all Verdrillmasten have been removed from that line over time.
  - petertodd 6y ago
    TIL too! The German wikipedia articles are quite detailed: https://de.wikipedia.org/wiki/Verdrillmast https://de.wikipedia.org/wiki/Verdrillmast https://de.wikipedia.org/wiki/Verdrillschema https://de.wikipedia.org/wiki/Verdrillschema I'd be interested to know if the twists have been removed from the lines. It might be the case that they've replaced the special twisting masts with other ways of twisting, eg taking the lines into a substation and re-orienting them on the way back out. If they've added a lot of substations as the land gets developed more, that may be the case. Also, I'm sure twisted masts are a bit more expensive. So this might just be a gradual process of saving money as equipment gets replaced rather than any specific engineering goal. There's many other things that unbalance lines, and twisting masts may not make enough of a difference compared to other issues.
    - zaarn 6y ago
      The lines themselves basically do not have twists anymore, it only happens at the special power poles (Verdrillmasten) and only statically (so no moving parts like in PGE/CA). They're more modern and safer but more expensive when you need to change infrastructure resulting in a different load on the 3-phase, so you have to rewire those towers. The upside is that rewiring them is somewhat safe and easy since you don't have to do it over the entire length between towers, only a few dozens meters on a single tower. edit: quite a few places also use single-level masts, that don't have this issue at all.
      - petertodd 6y ago
        Wait, that doesn't sound right. It's a bit hard to tell with Google translate. But from what I see on the wikipedia article (https://de.wikipedia.org/wiki/Verdrillmast https://de.wikipedia.org/wiki/Verdrillmast) Germany is doing exactly the same thing as is done in the US - the US does not twist lines in midair. Only at poles. What do you mean by "moving parts"? The US lines don't have any parts that move more than slightly, which EU lines do as well (they have too: the lines themselves expand and contract, and move in the wind, so the insulators have to have flexibility).
himinlomax 6y ago
You don't see those hooks things in Europe because I doubt we have any high voltage lines that old left. I suspect this one survived that long because of the much drier California climate.

petertodd 6y ago

Swapping the wires around at the start or end of the line doesn't swap them frequently enough. It's actually quite like a twisted pair in an ethernet cable: you swap the order frequently to average out the different position-dependent electrical characteristics to get a uniform characteristic. The EU probably does that less frequently simply due to higher density, and thus fewer long stretches of transmission line. I've personally seen a transposition tower in the EU on a line running across a mountain, so they do exist. https://en.wikipedia.org/wiki/Transposition_tower https://en.wikipedia.org/wiki/Transposition_tower

formerly_proven 6y ago
TIL. Germans of course have their Verdrillschemata to place Verdrillmasten properly, but it seems they're quite rare. There's a Wikipedia article with an example transmission line, but it notes that all Verdrillmasten have been removed from that line over time.
- petertodd 6y ago
  TIL too! The German wikipedia articles are quite detailed: https://de.wikipedia.org/wiki/Verdrillmast https://de.wikipedia.org/wiki/Verdrillmast https://de.wikipedia.org/wiki/Verdrillschema https://de.wikipedia.org/wiki/Verdrillschema I'd be interested to know if the twists have been removed from the lines. It might be the case that they've replaced the special twisting masts with other ways of twisting, eg taking the lines into a substation and re-orienting them on the way back out. If they've added a lot of substations as the land gets developed more, that may be the case. Also, I'm sure twisted masts are a bit more expensive. So this might just be a gradual process of saving money as equipment gets replaced rather than any specific engineering goal. There's many other things that unbalance lines, and twisting masts may not make enough of a difference compared to other issues.
  - zaarn 6y ago
    The lines themselves basically do not have twists anymore, it only happens at the special power poles (Verdrillmasten) and only statically (so no moving parts like in PGE/CA). They're more modern and safer but more expensive when you need to change infrastructure resulting in a different load on the 3-phase, so you have to rewire those towers. The upside is that rewiring them is somewhat safe and easy since you don't have to do it over the entire length between towers, only a few dozens meters on a single tower. edit: quite a few places also use single-level masts, that don't have this issue at all.
    - petertodd 6y ago
      Wait, that doesn't sound right. It's a bit hard to tell with Google translate. But from what I see on the wikipedia article (https://de.wikipedia.org/wiki/Verdrillmast https://de.wikipedia.org/wiki/Verdrillmast) Germany is doing exactly the same thing as is done in the US - the US does not twist lines in midair. Only at poles. What do you mean by "moving parts"? The US lines don't have any parts that move more than slightly, which EU lines do as well (they have too: the lines themselves expand and contract, and move in the wind, so the insulators have to have flexibility).

himinlomax 6y ago

You don't see those hooks things in Europe because I doubt we have any high voltage lines that old left. I suspect this one survived that long because of the much drier California climate.