Mains Voltage variation within North America?

[tcmtech]

surely such areas are simply fed from appropriate taps on sub-station transformers? - there's no excuse for not providing decent voltages at both extremes.

Not always.

For us rural dwellers the power just normally comes out of the substations as a single 7200 volt feed and go for miles, some times 20 -30 miles, with a simple two conductor single phase or four conductor 3 phase overhead or underground line set out to the many homes and end users.

If the voltage drop is bad enough at the substation they will change taps to raise the output voltage there but still everyone is basically on what comes down to being just a really really long extension cord and how stable your line voltage is is directly proportional to where you are and how much load there is at any moment.

I for one am close to a new and rather large primary three phase feeder line that is double fed now from two substations so my voltage is generally quite stable regardless of how much power I draw even during occasional bursts into the 40+ KW range when my big shop equipment starts up while other high draw devices are running.
However if I tried running my same loads at a buddies place who is at the far end of a long single phase feed put in back in the 1950's there would probably be severe voltage dip issues large enough to affect numerous neighbors up to a few miles away from his place.

 

[Nigel Goodwin]

Not always.

For us rural dwellers the power just normally comes out of the substations as a single 7200 volt feed and go for miles, some times 20 -30 miles, with a simple two conductor single phase or four conductor 3 phase overhead or underground line set out to the many homes and end users.

If the voltage drop is bad enough at the substation they will change taps to raise the output voltage there but still everyone is basically on what comes down to being just a really really long extension cord and how stable your line voltage is is directly proportional to where you are and how much load there is at any moment.

I for one am close to a new and rather large primary three phase feeder line that is double fed now from two substations so my voltage is generally quite stable regardless of how much power I draw even during occasional bursts into the 40+ KW range when my big shop equipment starts up while other high draw devices are running.
However if I tried running my same loads at a buddies place who is at the far end of a long single phase feed put in back in the 1950's there would probably be severe voltage dip issues large enough to affect numerous neighbors up to a few miles away from his place.

That's still no excuse

If a feed is too small (and a 1950's feed could well be far too small by now) then it needs upgrading. If it's going 20-30 miles it would obviously benefit from a higher voltage line.

There was a situation in Matlock (where I work) where a LOT more houses were built at the end of a road with an underground feed (as most UK wiring is underground) - this caused low mains supply problems, because it was never designed to carry that load. The solution, fairly obviously, was to dig the road up and run more suitably rated cabling.

The company I work for closed one of our shops a couple of years ago (it wasn't doing much business, as it's in a mostly tourist town), and we now rent it out. Behind the shop (the other side of a car park) was the service department, and this has been converted in to two apartments (there's also two big wooden garages - these are planned to be knocked down and a further apartment built - if/when planning permission can be obtained). The workshop obviously only had a single mains feed, and a single meter, so we asked for a second meter to be fitted - to be told that for this to be done we would have to pay to have the underground cable replaced as it's not large enough to feed two meters. As this would cost about £20,000, and cause utter chaos (as it would prevent access to the car park and the other businesses around).

So in the meantime both apartments are fed from a single meter, and the owners pay the electricity bills - with the rent on the apartments adjusted accordingly.

Bit of a bodge, but it works for now Presumably, if the further build goes ahead we would have to have the supply replaced - but as it stands there's no low voltage problems at all, just an electricity board requirement to meet modern standards rather than the standards when it was installed.

 

[tcmtech]

That's still no excuse

If a feed is too small (and a 1950's feed could well be far too small by now) then it needs upgrading. If it's going 20-30 miles it would obviously benefit from a higher voltage line.

You get what your given you unless you want to pay for the new systems yourself.

Around here the higher population areas get priority on the system upgrades, which my local utility has been excellent about for as long as I can remember being its customer owned, but still if you are out in the middle of the prairie and the next nearest person is 10 miles away you are naturally going to be very low on the upgrades list unless you have a record of burning a lot of power and are a financially justifiable expenditure for them.

Around here most people complain about the price of a 50 foot 12 ga extension cord. Imagine what they would do if they got the bill for ten miles of 2/0 HV underground cable plus the install fee!

 

[Sceadwian]

Next thing you know we'll be blaming the power companies for not making cables out of pure silver or better yet super conductor distribution systems.

 

[johansen]

Next thing you know we'll be blaming the power companies for not making cables out of pure silver

lol i'm sure some folks on diy audio are!

 

[Sceadwian]

They might johansen, but they're too busy with their room acoustic equalization chambers. (randomly built wood boxes)

 

[audioguru]

I agree that people who live far from civilization get poor utilities. Some of them do not even have sewers so they dump their poop into a tank in their yard. YUCK!

 

[ronv]

The grass is always greener on the other side of the septic tank.

 

[Mr RB]

...
As for Mr RB's point about 'end of line' and 'close to substation', surely such areas are simply fed from appropriate taps on sub-station transformers? - there's no excuse for not providing decent voltages at both extremes.

Yeah Tcmtech already covered it but essentially the power line is like a long string of resistors with clients inbetween.

They can balance it somewhat by the transformer taps, but the load changes with the daily peaks etc and so does the voltage on your street (but the transformer taps don't) so depending where you live it might be ok for part of the day then too high or too low at other parts of the day.

In the UK you have a much higher population per km of distribution, so in a denser network like that there are more transformers and more regulation for less distance of "resistors". You also likely have a much higher $ density per km of distribution, so that pays for a slightly better standard of service too.

 

[johansen]

Yeah Tcmtech already covered it but essentially the power line is like a long string of resistors with clients inbetween.

close, but large >25KW transformers have impedances that exceed the resistance, often by a factor of 2 or more.
for example, a 500KW transformer may have an impedance of 5.5% but an efficiency of 98 or more %

additionally, the wavelength of the transmission line can cause a +/-2% voltage rise or fall due to the transmission line effect and the power factor.

the largest transformers are 99.5%+ efficiency but they have an impedance of 15-20%.

it really is quite an art to keep the voltage stable everywhere....