US Power grid overview? - Page 1
Forum section: electronics / general

author: justinjja
author_rank: Regular Contributor
timestamp: July 05, 2020, 02:56:55 pm
content: In my area we have huge towers running above ground lines, that seem to be point-to-point type connections.Then we have regular pole power lines that typically follow large roads.These then connect to substations, after which the power goes underground in residential areas.Each neighborhood then has a couple large truck sized pad transformers, serving maybe 1000 homes.Then every street has smaller 100kw transformers serving about 10 homes each.I know I get 240v split/single phase to my house,I'm sure the huge towers are running 100kv+ 3 phase, probably from power plants.But what all is likely in between,Where would you guess 3 phase ends? What voltage do you thing everything would run at? What voltage runs along my street feeding the 100kw transformers?Edit:Found this which gives me a good idea for the above gound stuff:https://www.osha.gov/SLTC/etools/electric_power/illustrated_glossary/transmission_lines.htmlStill curios about the undergound voltages, and 3phase.I guess it would make sense if the small 100kw transfomers are fed by 7-13Kv "distribution"And the larger transfomers are 34-69kv "subtransmission"

author: David Hess
author_rank: Super Contributor
timestamp: July 05, 2020, 05:40:51 pm
content: I think it is 3-phase up until the last transformers which power groups of houses, at least that is what I see on the string of power poles behind my house. The transformers for the groups of houses are attached to different phases to balance the 3-phase load.

author: Gregg
author_rank: Super Contributor
timestamp: July 05, 2020, 07:09:38 pm
content: You may be interested in watching a few videos from a Canadian lineman:https://www.youtube.com/channel/UCpJWHeFjOjoDrHLIPqIHgwAAlthough he is in Canada, the systems are very similar.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 06, 2020, 03:43:59 am
content: 3-phase ends somewhere between neighborhood distribution, and the building.Often, residential neighborhoods are wired between two distribution phases, or one phase and neutral; the entire neighborhood is in phase, and the e.g. 4800V is stepped down to 240VCT as needed.If you see three (none grounded) or four (possibly one grounded) distribution lines, chances are they're carrying 3-phase. Easily confirmed where a commercial customer has all three phases hooked up, either to a much fatter or taller pole pig, or two or three pigs together. (Harder of course to tell on pad transformers, though there may be a placard on the outside indicating what type of transformer it is.)My neighborhood for instance is the first kind, and I'm also aware that it has a single-action recloser (at the substation, or along the way), because the power seems to go out about every summer, plus very windy days any point in the year. When it does, it comes back briefly a few seconds later, then doesn't try any further and remains dead for an hour as crews are dispatched. Then either it's back, or if the manual reclose fails, another hour as they search the line for faults.Alas, such is the reality of overhead wiring (and a certain degree of lacking infrastructure automation).I guess this is a good reason to have commercial and industrial zoning, to save on materials; or, a good reason to have 3-ph everywhere, and loose or no zoning, like Europe does it.Tim

author: Berni
author_rank: Super Contributor
timestamp: July 06, 2020, 06:01:44 am
content: The pole pigs have the primary connected across two of the 3 phases. The dual secondary of the pole pig then creates the two split phases.But there are some cases where 3 phase is masqueraded as split phase. This is where the 208V comes from. Instead of connecting proper split phase to the 240V sockets they just connect two of the 3 phases to the socket and pretend its 'split phase'. Most loads don't care if its getting 208 or 240V so its fine.In Europe we don't have any of this. We simply run 3 phase 240V from the big transformer down the whole street and tap it off directly at each house. But in some places you can find giant polepigs that can service a small street(also 3 phase)

author: duak
author_rank: Super Contributor
timestamp: July 06, 2020, 09:44:46 pm
content: I have 14.4 kV, 3 phase running right in front of the house - we have no rear alley. When the utility renewed the poles, probably dating from 1950, they also went from 40' to 50'. This area was first built with single and two storey houses; replacement houses are 3 storey McMansionoids so it makes sense they would increase the pole length. Cable and telephone also share the poles and they've been adding their own stuff below the power.The utility also wanted to strengthen their grid so they had planned an underground 230 kV line nearby as their Right of Way was full. I went to their consultaion open house, talked with one of their engineers and looked at a sample of the cable. I think she said the current was in the 2,000 A range. They were also planning to lay 4 conductors with one as a spare.