House voltage

[koneguitarist]

My house voltage seems to be about 245V , is that too high or is there allways + - discrepancy and how much is normal ?

[octatonic]

+/- 10% is pretty normal.

[jpfamps]

UK mains "used" to be 240V + 6%/-10%.

The UK is now "officially" 230V to comply with the harmonized EU standard, however the tolerance is 230V +/- 10%, so miraculously our old standard fits within the new EU standard, and we don't have to change our generating infrastructure.

Mains is legally allowed to rise to 253 VAC, so 245 VAC is well within spec.

The mains in our workshop is usually about 245 VAC and rises to 250 VAC in the evenings.

[koneguitarist]

does this voltage variance affect amps much and if so how ?

[deano_l]

Generators also have an obligation to keep the AC frequency with quite tight tolerances, not just the voltage. That's why turbines rotate at around 3000 RPM, because if you divide that by 60 you get the 50 cycles per second (Hz) AC frequency that the electricity comes into your house at.

It varies a little bit as well, but not by anything like the swings in voltage.

[musophilr]

Generators also have an obligation to keep the AC frequency with quite tight tolerances, not just the voltage. That's why turbines rotate at around 3000 RPM, because if you divide that by 60 you get the 50 cycles per second (Hz) AC frequency that the electricity comes into your house at.

It varies a little bit as well, but not by anything like the swings in voltage.

IIRC that's because there are some timing devices that work by counting AC cycles, and they're obliged to generate the right number of cycles in a 24 hour period. So if they're been running slow they speed up a bit to catch up, hoping it all comes out in the wash.

[jpfamps]

IIRC that's because there are some timing devices that work by counting AC cycles, and they're obliged to generate the right number of cycles in a 24 hour period. So if they're been running slow they speed up a bit to catch up, hoping it all comes out in the wash.

The reason the cycle of the mains is tightly controlled is because you need to synchronize all generators connected to the grid otherwise you are simply wasting power.

[deano_l]

That's right. The frequency is related to the load on the grid. If the load increases for some reason, the generators will continue to rotate at their current frequency and the frquency of the AC current will decrease. Most power plants have automatic monitoring and if this happens they will speed up the turbines to increase the frequency, but that can take a couple of minutes due to the inertia in the rotating masses in the turbines and generators. They are big buggers and they dont speed up or slow down very quickly.

Anyway, the point is that you can't rely on the voltage or frequency coming into your house, except within some defined tolerances. Simply due to the nature of the beast. Generating and transmitting electricity is dependant upon many factors, all of which can have an affect on the quality of power coming into your house.

If you need absolute guarantee's, I believe you can buy power conditioners that will remove the variability. You plug that into the mains, and your amp into the conditioner.

[Cirrusband]

IIRC that's because there are some timing devices that work by counting AC cycles, and they're obliged to generate the right number of cycles in a 24 hour period. So if they're been running slow they speed up a bit to catch up, hoping it all comes out in the wash.

Yep, and there's a website somewhere that tells you in real time what the frequency is and what the average was over a set period.

It's a very boring page.

[ICBM]

The voltage depends on distance from the substation as well as the load on the chain from there. I typically get about 235 here out in the semi-sticks (must ask some friends who live actually in the middle of nowhere what theirs is!), and it varies with time of day and sometimes minute to minute - but in the shop in central Glasgow that's right next to the substation, it's almost always at 250 or just over. Which at least guarantees that anything I test in the shop will hold up at gig voltages as well .