Low Mains Voltage (~190-220v) - How to resolve?

[UNG]

@phil d

that’s where load curtailment and using your EV as electric storage to feed in comes into play

That is where the theory sounds good and the practical reality has the potential to cause problems for some if not all

LOL.... it's going to be a long time before we have that kind of problem I'd expect,,,, and if that were the case then I'd expect people to have multiple charging points or one that can supply multiple vehicles (with load curtailment)..... but I know what you mean  I had it today after carrying out an EICR,,, kids come home from school "MUUUUUM... the internet isn't working!".. luckily I'd finished so I told them to plug it back in

That long time is not too far away if the green lobby gets it's way, the next 10 - 15 years could be interesting in how technology develops to meet the demand as we are forced to ditch ICE cars and gas heating

 

[NozSpark]

That long time is not too far away if the green lobby gets it's way, the next 10 - 15 years could be interesting in how technology develops to meet the demand as we are forced to ditch ICE cars and gas heating

Hence why I'm doing my EV course next week.... 

 

[toontoonizer]

Another update: got the multimeter and measured this at the supply cutout just now:

210v at a 56A load

207v at a 60A load

Something not quite right

 

[Sharpend]

Can I suggest you switch off all your consumer units and test at supply again? 
 

did you get your clamp meter for Amps? 
 

Where in the country are you? 

 

[ProDave]

Another update: got the multimeter and measured this at the supply cutout just now:

210v at a 56A load

207v at a 60A load

Something not quite right

That would imply a supply impedance of 0.5 ohm.

That would also imply if load was reduced to zero, the supply voltage would be 237V

If the load was 100A you would expect it to drop to 187V

I would regard a loop impedance of 0.5 ohm as high, typically even in rural properties I see not much more than half that.

 

[toontoonizer]

Can I suggest you switch off all your consumer units and test at supply again? 
 

did you get your clamp meter for Amps? 
 

Where in the country are you? 

Can't turn off all the consumer units at the moment but will do when I can. Yep using a clamp meter for amps around the live cable coming directly out of the 3 phase cutout. 

Voltage probes on the negative and live Henley blocks (which is where the DNO also measured it)

We're in theydon Bois in epping. 

That would imply a supply impedance of 0.5 ohm.

That would also imply if load was reduced to zero, the supply voltage would be 237V

If the load was 100A you would expect it to drop to 187V

I would regard a loop impedance of 0.5 ohm as high, typically even in rural properties I see not much more than half that.

Just went up to 90A and I read 193.8v

Nothing to do except wait and see what the DNO do. They were saying another voltage logger. It will be the same guy as last time most likely and he said it wasn't their problem so....not sure how that will go. 

 

[ProDave]

With eratic readings like that,. it would be interesting if you can get a period where you can turn everything off for a while, to plot the no load voltage over a period of time.

Chances are the no load voltage is going up and down, as the load in neighbouring houses varies as well.

Question: does asyone know the maximum permissible supply loop impedance at the origin?

 

[phil d]

With eratic readings like that,. it would be interesting if you can get a period where you can turn everything off for a while, to plot the no load voltage over a period of time.

Chances are the no load voltage is going up and down, as the load in neighbouring houses varies as well.

Question: does asyone know the maximum permissible supply loop impedance at the origin?

here's an interesting document from one of the network operators

https://www.spenergynetworks.co.uk/userfiles/file/EART-01-002.pdf

 

[ProDave]

here's an interesting document from one of the network operators

https://www.spenergynetworks.co.uk/userfiles/file/EART-01-002.pdf

Useful document, thanks.

That states for a 100A PME supply the maximum acceptable earth loop impedance is 0.35 ohm, so if my rough estimate from the figures a few posts above of 0.5 ohm is correct, this supply us non compliant.

 

[Sidney]

I'll have to dig it out but the requirement for the 0.35 ohm limit is for new supplies, IIRC existing can go up to 0.8 before they'll do anything about it. This is buried in an ENA document somewhere...

 

[toontoonizer]

Useful document, thanks.

That states for a 100A PME supply the maximum acceptable earth loop impedance is 0.35 ohm, so if my rough estimate from the figures a few posts above of 0.5 ohm is correct, this supply us non compliant.

I'll have to dig it out but the requirement for the 0.35 ohm limit is for new supplies, IIRC existing can go up to 0.8 before they'll do anything about it. This is buried in an ENA document somewhere...

Ah getting the hopes up and then down again .

I did another test to assess the voltage drop between the supply and annex. 

Checked the annex voltage with both multimeters to assess for differences in calibration - both meters showed the same voltage so differences were within margin of error. 

Put voltage probe on the supply live and neutral Henley blocks and a probe on the annex's consumer unit IN live and neutral. 

I measured 209v at the supply and 207v at the annex with a 40A load on the annex SWA only. Total load on the supply was 60A. 

So that's a 2v drop across the SWA run from the supply to the annex consumer unit. 

 

[Murdoch]

I measured 209v at the supply and 207v at the annex with a 40A load on the annex SWA only. Total load on the supply was 60A. 

So that's a 2v drop across the SWA run from the supply to the annex consumer unit. 

how far away is the annex from the house? 

distance, load and volt drop are to be expected ...............

 

[toontoonizer]

how far away is the annex from the house? 

distance, load and volt drop are to be expected ...............

Yup totally get that, I was just expecting more . 

It's about 30 meters away...but the cable has to go a more roundabout route so that's prob 50-60m. 

 

[toontoonizer]

UPDATE: The 3 phase meter is installed and we have distributed the annexes to one on each phase. 

While overall, the voltage tends to bottom out at 210v so this is an improvement. Not ideal though as we are still getting significant voltage drops at the supply. 

No update from DNO as to what they are doing about it. 

 

[Murdoch]

UPDATE: The 3 phase meter is installed and we have distributed the annexes to one on each phase. 

While overall, the voltage tends to bottom out at 210v so this is an improvement. Not ideal though as we are still getting significant voltage drops at the supply. 

No update from DNO as to what they are doing about it. 

who is we?

 

[toontoonizer]

who is we?

Our electrician

 

[Murdoch]

Our electrician

so this is the first time you’ve mentioned an electrician. What does he suggest?

 

[toontoonizer]

so this is the first time you’ve mentioned an electrician. What does he suggest?

He agrees that is likely an issue with the supply.

On a side note, our new meter is saying we have used 300kWh a day since it has been installed. So over 8 days. 

This works out to £1,000 a month for electricity - and is over triple what we paid before the meter exchange. I can't fathom how we would be using 300kWh a day. Our usage hasn't changed, only that we have a 3 phase meter. 

Any chance the potential supply issue is affecting the meter reading? Or, even more unlikely, the meter has some issues?

 

[Murdoch]

On a side note, our new meter is saying we have used 300kWh a day since it has been installed. So over 8 days. 

This works out to £1,000 a month for electricity - and is over triple what we paid before the meter exchange. I can't fathom how we would be using 300kWh a day. Our usage hasn't changed, only that we have a 3 phase meter. 

300kwh per day, ouch, that’s nearly what we use per month!

you growing drugs ?

seriously that is huge consumption- what are you doing?

 

[SPECIAL LOCATION]

Or is it possible that a comprehensive test of the whole installation, inc all final circuits has not been made..

and you do have some faulty kit somewhere drawing far more than you thought?

Hence, more load more volt-drop!?

On an earlier post I think you said you have no electrical certificates for any parts of your installation..

Ha electrical certificates? No idea where those would be. If they didn't come with the house when we bought it then they don't exist.

Have you asked your electrician verify the condition of all circuits?

On the balance of probability you would have to assume the New-Meter is good?

:C