255v - stopping ev charger

[RogTP]

We have a problem with voltage being too high for our EV Charger, it goes to about 255v regularly and we know the charger trips at 253. We have spoken to DNO at length and they want to put a new line into the house, which while mostly at their cost will cause enormous disturbance and some cost to us (new meter box needed and tails running to consumer unit, etc).

All we need to do is drop the voltage to the charger by 3 volts. I know a voltage optimiser would work. Is there any recommendations for one that would do the job? 32A charger so I think a 63A would cover it. We can place it so doesn't need to take whole house load.

 

[Andy™]

We have a problem with voltage being too high for our EV Charger, it goes to about 255v regularly and we know the charger trips at 253. We have spoken to DNO at length and they want to put a new line into the house, which while mostly at their cost will cause enormous disturbance and some cost to us (new meter box needed and tails running to consumer unit, etc).

All we need to do is drop the voltage to the charger by 3 volts. I know a voltage optimiser would work. Is there any recommendations for one that would do the job? 32A charger so I think a 63A would cover it. We can place it so doesn't need to take whole house load.

DNO putting a new cable into the house is not likely to fix the problem

 

[Murdoch]

Why do they think you need new cables from the meter to the CU? and I doubt the DNO would actually do that too

 

[binky]

More likely a transformer fault - needs adjusting down

 

[NozSpark]

Voltage optimisers are a pretty common fix for over voltage in these circumstances… Thankfully I’ve not had to fit one yet and I’ve not paid attention to the ones that I’ve seen

 

[Andy™]

Voltage optimisers are a pretty common fix for over voltage in these circumstances…

not looked into them for a while but they used to only be good for small loads and would bypass on larger loads like a shower, so it would do the same with a car then you're back to higher voltage and switching off

 

[RogTP]

The line from the pole is quite long at 49m, and it seems the DNO would prefer it was nearer to 20m. They can't get it to 20m, because the house is simply too far from the pole. So they want to put in a heavier weight cable, presumably to provide a more reliable connection and I believe to reduce circuit resistance. Because new cable would be heavier, it would need to be trenched rather than run across neighbours house as before.

The high voltage is almost always, but not exclusively, over night, so is not caused by PV loading. DNO comes and tests during the day, so aren't capturing what is happening at pole and house when voltage is high.

I've suggested to them turning the transformer down, but they really don't seem keen. They seem more keen spending £10k-£20k trenching a new cable. I've suggested to them supply a voltage optimiser, again they aren't keen because it patches over a potential 'network problem'.

 

[RogTP]

I should add, new meter and tails is because the existing meter is no longer on an external wall (extension built over the entry point 20 years ago). So DNO wants a new meter box.

 

[binky]

The line from the pole is quite long at 49m, and it seems the DNO would prefer it was nearer to 20m. They can't get it to 20m, because the house is simply too far from the pole. So they want to put in a heavier weight cable, presumably to provide a more reliable connection and I believe to reduce circuit resistance. Because new cable would be heavier, it would need to be trenched rather than run across neighbours house as before.

so too high a resistance for the size of cable, that can cuase higher voltages when backfeeding soalr to the grid. Not asure about when pulling enrgy from the grid.

The high voltage is almost always, but not exclusively, over night, so is not caused by PV loading. DNO comes and tests during the day, so aren't capturing what is happening at pole and house when voltage is high.

does suggest 'sticky taps' in the transformer.

I've suggested to them turning the transformer down, but they really don't seem keen. They seem more keen spending £10k-£20k trenching a new cable. I've suggested to them supply a voltage optimiser, again they aren't keen because it patches over a potential 'network problem'.

if it's not costing you anything (and it shouldn't) then it's their gear to do with as they see fit.

Voltage optimisers ae not something they would use, better they fix the network issue than install a VO.

 

[RogTP]

@binky thanks for the response.I agree I don't think they will got for the VO. The implication is it will cost me for the new tails from new meter box to consumer unit, potentially a complex route. I will of course state this should be picked up by DNO.

The route they are proposing (but still to be agreed), potentially means cutting down two holly trees in a conservation area. So not just the financial cost at issue. And no guarantee it will fix the problem.

 

[RogTP]

Just had more correspondence. They are not keen to tap down at the pole transformer, since it seems they must switch off the whole area, which unsurprisingly they aren't keen to do.

If I'd have known getting an EV charger working reliably would take this much effort, I wouldn't have bothered.

 

[Andy™]

Just had more correspondence. They are not keen to tap down at the pole transformer, since it seems they must switch off the whole area, which unsurprisingly they aren't keen to do.

If I'd have known getting an EV charger working reliably would take this much effort, I wouldn't have bothered.

its their poblem to fix. if they want to waste money doing all that work to replace cables then le them get on with it. since its a fault on their side you can tell them they are responsible for all associated work inc anything on your side of the cutout since it only needs done to fix their problem

 

[binky]

Just had more correspondence. They are not keen to tap down at the pole transformer, since it seems they must switch off the whole area, which unsurprisingly they aren't keen to do.

If I'd have known getting an EV charger working reliably would take this much effort, I wouldn't have bothered.

You have probably saved some of your appliances from an early death to boot. It my well be a pain in the neck, but, ultimatley you have found a fault with your supply that needed fixing. Had this a few times with solar inverters finding grid voltages are too high, or float high at certain times of day.

 

[UNG]

When you get threads like this where the supply voltage is an issue because it exceeds the upper 253v limit I do wonder has the DNO's attitude to voltage harmonisation played a part in creating the problem they now have, it's nearly 30 years since the EU voltage harmonisation was instigated and very little has been done to move the nominal voltage down across the supply network to the 230v level, even back in the 90's I attended a few DNO events on the subject and the concensus was the network will still work as it is so we won't do anything unless we need to repair or upgrade the existing equipment. Moving on I know of a number of areas where distribution equipment has been replaced or upgraded in the last 10 years and the voltage still remains 10 - 15v above the 230v nominal level or to be more precise at the levels it was at in the mid 90's, the additional problem the network has now is the uptake of solar PV which is generally pushing the network voltages up and there isn't much margin to play with before the 253v limit is overrun

 

[RogTP]

In the conversations I've been having, they seem worried about dropping off the bottom, 216v, on longer runs, so they same they are trying to keep it as near to 253v as possible. This gives absolutely no headroom for getting it wrong. Not aiming for 230v at all.

 

[binky]

In the conversations I've been having, they seem worried about dropping off the bottom, 216v, on longer runs, so they same they are trying to keep it as near to 253v as possible. This gives absolutely no headroom for getting it wrong. Not aiming for 230v at all.

that would suggest the network in your area needs upgrading. The highest voltages I have seen are in Plymouth city centre, where they have been building high rise flats.

 

[michael8554]

I'm missing something here.

Won't a lower resistance cable to the house equal lower voltage drop equals even higher voltage at the house ?

 

[UNG]

In the conversations I've been having, they seem worried about dropping off the bottom, 216v, on longer runs, so they same they are trying to keep it as near to 253v as possible. This gives absolutely no headroom for getting it wrong. Not aiming for 230v at all.

If they need to keep the network voltage as close to 253v as possible it would suggest that there is a problem in the network whether it is the design or the distribution equipment is not able to cope because of the addition of new builds in the local area, the only other thing is this a seasonal issue and the local transformer auto taps are setup for winter loadings where there will be potentially a lot more heating load in use

The most noticeable transformer tapping issue I've ever seen was on a factory with an 11Kv incomer the transformers had been replaced which the factory engineering team took as routine maintenance works, at the time we were the CCTV maintenance contractor and it was done a fixed price, we started to notice that we were using a lot more lamps for the IR illuminators which at £30 each starts to add up when the lamp replacement goes up by 250 - 300% compared to the previous 3 - 4 years, we approached the site electrical engineer to highlight this problem but were assured nothing had changed onsite, the problem was found a few months later late on a Saturday night / Sunday morning when I was called out because a couple of the cameras had gone off in on critical areas of the factory boundary I got to one camera and the supply voltage was at 278v went back to check on Monday morning and the voltage was back to 242v then it was back to the site engineer who had one of those moments where the penny dropped, the new transformers fitted 10 months earlier were causing the problem and this coinsided with when or lamp usage went up

It would be interesting to install a power analyser for a few months to see how much the voltage varies over that period to see if there is any trend or time where the voltage drops by 20 - 30v to justify the DNO reasoning for keeping close to 253v, even if they tried to keep around 240 - 245v that woul still give a buffer of a 23 - 28v drop before the lower limit was breeched which should be easily enough to manage the network properly

 

[RogTP]

I'm missing something here.

Won't a lower resistance cable to the house equal lower voltage drop equals even higher voltage at the house ?

That's what I would have thought.

 

[Andy™]

I'm missing something here.

Won't a lower resistance cable to the house equal lower voltage drop equals even higher voltage at the house ?

yes, which is why i doubt that would work. on the plus side it'll make it even worse so maybe more likely to get fixed properly?