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| richard.cs:
--- Quote from: james_s on July 02, 2020, 09:20:02 pm ---Underground wiring is far more expensive to install and maintain than overhead. While it's true that it isn't as prone to damage in wind storms that knock trees down it's not immune, a root ball from a fallen tree can really do a number on underground wires. It's also far more prone to damage from flooding and tremendously more difficult to troubleshoot and repair. It works well in areas that are dry and have relatively few trees though. --- End quote --- I am with you on more expensive to install but unconvinced on underground cable maintenance being more expensive than overhead, at least in a UK-like climate. Sure it costs more to actually do the repair but it is rare. Here underground cable faults are more often from people digging them up by accident* than by tree roots and similar though it does happen. Failures not caused by digger buckets are often poorly installed joints or places where the cable sheath was nicked on installation leading to eventual to water ingress. I don't see why the cables themselves would be considered vulnerable to flooding? They're waterproof and often installed below the water table anyway. A majority of all the underground cables ever installed in the UK are still in service, thousands of miles of 1950s lead-covered cable still in-use. In comparison we loose lots of overhead cables every time there's a storm and routine maintenance is needed too - regular tree cutting, replacement of the poles every 30 years or so, etc. Generally I expect our electricity suppliers to do the cheapest thing, and they seem to have settled on putting new cables underground by default in urban and suburban areas. This may be influenced by them being fined for customer minutes off supply, so powercuts have a significant financial cost. *Yes someone pays to fix these (and other expenses incurred as a result), but it's not the cable owner. |
| TimFox:
Yes, everything in engineering involves a trade-off between installation cost and operating cost. It depends on how much it costs to repair ice-storm damage, and often it occurs, and if the power company is liable for consequent damage. New York City banned overhead wires sometime after a serious blizzard in 1888, although there are still some areas in the city (annexed thereafter) with overhead wires. |
| themadhippy:
--- Quote --- It's also far more prone to damage from flooding and tremendously more difficult to troubleshoot and repair. It works well in areas that are dry --- End quote --- meanwhile in the uk we run 400KV cables under the towpath and use the canal water to keep the cables cool |
| IanB:
--- Quote from: richard.cs on July 02, 2020, 10:19:32 pm ---Generally I expect our electricity suppliers to do the cheapest thing, and they seem to have settled on putting new cables underground by default in urban and suburban areas. --- End quote --- In the UK I would think this is more about planning consent than cost. When there is a new development every detail has to be negotiated with the planning authority, and I would assume that "all cables are underground" is high on the list of requirements. Weirdly, not long ago the National Grid were upgrading a substation near where I grew up (I used to fall asleep every night to the transformer hum floating miles across the countryside--but I digress), so anyway they were upgrading the substation and they actually did a public consultation about the design of a new switch yard--air insulated circuit interrupters or gas insulated interrupters. The air breakers were bigger, required more land area, but were cheaper and easier to maintain, while the SF6 breakers were more compact and had a smaller footprint, but were more expensive. People voted for the SF6 design, and they accepted the result of the poll. I was surprised they actually did that consultation exercise. |
| james_s:
--- Quote from: themadhippy on July 02, 2020, 10:46:47 pm --- --- Quote --- It's also far more prone to damage from flooding and tremendously more difficult to troubleshoot and repair. It works well in areas that are dry --- End quote --- meanwhile in the uk we run 400KV cables under the towpath and use the canal water to keep the cables cool --- End quote --- How many junctions, switches, fuses, and transformer vaults are down there under the canal water? How much does it cost to maintain them? Do you think the UK possesses some magical technology that North America lacks? Keep in mind the entire country is smaller than some of our individual states, there has got to be a lot less electrical infrastructure, vastly fewer km of cable. This is one source I came across: "According to the May 2011 paper “Underground Electric Transmission Lines” published by the Public Service Commission of Wisconsin, “The estimated cost for constructing underground transmission lines ranges from 4 to 14 times more expensive than overhead lines of the same voltage and same distance." Underground lines have their place, they have advantages, but they also have disadvantages. Because of that we typically use underground in cities and modern suburbs but the long runs between towns are usually overhead. |
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