General > General Technical Chat

The US electrical system

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richard.cs:

--- Quote from: james_s on July 03, 2020, 04:38:29 am ---
--- Quote from: themadhippy on July 02, 2020, 10:46:47 pm ---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."

--- End quote ---

Here we make a distinction between "transmission" at >100 kV, "HV distribution" generally at 11 kV and 33 kV, and "LV distribution" at 400 V (all line to line).

The vast majority of our transmission network is overhead - at these voltage levels underground becomes very expensive, but in urban areas both HV and LV distribution tends to be underground, and there is very little suburban HV distribution.


--- Quote from: james_s on July 03, 2020, 04:38:29 am ---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.
--- End quote ---
Well yes, we tend to do that too, noting that "long runs" are always at higher voltages. The point I was making is that this kind of thing: https://goo.gl/maps/rqwRZZQkqCgEUxqQ6 with HV distribution on poles in a urban area just does not exist here at all.

tom66:
There are some 275kV cables that run under an office estate I used to work at in Leeds.  I'm not sure why they ended up there but I recall National Grid was pissed that someone had built an estate over this underground line.  They had assumed they would always be able to dig to access the cable!

themadhippy:

--- Quote ---How many junctions, switches, fuses, and transformer vaults are down there under the canal water?
--- End quote ---
none ,but then again no mention of those factors was mentioned by the claim

--- Quote ---It's also far more prone to damage from flooding
--- End quote ---

The added advantage is no road closures if a fault does occur,and the heat from the cables keep the tow path frost free

--- Quote --- with HV distribution on poles in a urban area just does not exist here at all
--- End quote ---
https://goo.gl/maps/zkvizUUCEwnNckxJ8

Monkeh:

--- Quote from: themadhippy on July 03, 2020, 02:46:14 pm ---
--- Quote --- with HV distribution on poles in a urban area just does not exist here at all
--- End quote ---
https://goo.gl/maps/zkvizUUCEwnNckxJ8

--- End quote ---

Well, they're not poles.. ;)

james_s:

--- Quote from: themadhippy on July 03, 2020, 02:46:14 pm ---The added advantage is no road closures if a fault does occur,and the heat from the cables keep the tow path frost free

--- End quote ---

I don't see how they avoid road closures if there's a fault, here they typically have to close at least a lane to excavate a faulty underground cable, sometimes it's quite a major project. There have been a few cases where underground transformer vaults have caught fire or exploded and left a crater in the street. If it's an overhead line the fault is usually a large tree falling across the line (and the road) so the road is closed while crews clear the tree, repairing the power lines doesn't normally require any sort of closure, they just park the utility truck on the shoulder and get to work. It doesn't really happen very often though, just when a big storm rolls through at which point there are often road closures all over from downed trees, most of which don't involve power lines.

Somebody posted this a few days ago https://www.youtube.com/channel/UCpJWHeFjOjoDrHLIPqIHgwA
He's based in Canada but their system is pretty much the same as what we use here in the US. Older and rural areas are typically exclusively overhead, newer, urban and/or more upper class areas that can afford the cost are usually underground.

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