Posted by: @transparent

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Hmm...

whereas I understand the physics behind grid topology and operation, and I know it's being threatened by political policies 😯 

We can't keep on being 'unfriendly' to the grid which supplies us, and expect to get away with it.
Spain is learning that the hard way as a result of their national outage on 28th April last year.

My motivation is resilience, rather than monetary.

Posted by: @papahuhu

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@transparent Yes, but I went through and followed the correct procedures. If the procedures are wrong thats for the electrical engineers to remedy. 
I can’t remember the last time we had a power outage, must be more than 8 years ago. Whereas in the 70s and 80s there were many. So something is working very well as is.

This seems to me somewhat analagous to personal tax obligations. 

No-one would argue that tax evasion is illegal (whether we agree or not about how appropriate the current tax rules are). However, reorganising one's financial affairs so as to pay less tax - tax avoidance - is generally regarded as a good and prudent thing to do. Nonetheless, this is not a simple matter of "right" or "wrong"; there's a spectrum in play. Jimmy Carr will attest that it's perfectly possible to be legal and inappropriate at the same time.

My view is that, both for tax and use of the National Grid, anything seen as inappropriate should be legislated against. Effectively, that's @papahuhu's point about amending the procedures. I also believe that, living with the practicalities of life, we should all be expected to show a degree of "moral common sense". I, for instance, am currently experiencing significant voltage issues that UKPN are investigating, so it would be inappropriate for me to ignore that when using my heat pump, home battery and EV even if I'm within my rights to switch them all on together and let grid stability be damned. I hasten to add there is no suggestion that @papahuhu has done anything inappropriate - and the close communication with his DNO underlines that - but @transparent's point about the need for greater co-ordinated management of the fluctuations is still well made. We collectively need to treat the grid more kindly.

Ultimately, I suspect we ought to go down the Continental route of 3-phase being the standard so that we don't need to get into the discussions of phase imbalance at a local level.

@transparent 

Although we don't export, we were offered 6kw (around 25A) export on our application with UKPN.

I suspect there may be some "local" calculations done to see if it is ok, so some may be offered more, some less?

@majordennisbloodnok 

I’m not in the trade, but I’d heard somewhere that there were plans under consultation to rollout 3P supply to a junction box outside all homes. Similar to the sort you see in the US. I don’t know if it has been approved nor the timeframe. 
I also don’t know whom they intend to take the cost for the new consumer unit, fuse, smart meters and connection to the house. 
I had an estimate prepared and it was £18k, I only did it because I was originally told I needed a 3P heat pump. It was a load of nonsense by the incompetent renewables industry. I had a 1P 16kW unit fitted and that’s proven to be way too powerful for the house, they had originally told me i needed 3P 24kW, useless clowns. 

You're right @bash - every G99 application gets assessed on the substation data available to the DNO.

There will be differing results, even for houses connected to the same local substation.
The cable distance between you and the substation matters, as do the number of other houses between you and the substation.

But DNOs will only know the phase to which each house is connected for around 10% of locations.
There is no universal requirement for phase connections to be recorded.

Moreover, only a few hundred of the 550,000 local substations have ever had monitoring systems connected to them.
The engineers are working blind.

UKPN is consistently approving larger export applications than other DNOs.

There may be technical reasons for this, such as the higher population densities found in SE England.
Cable supply lengths are shorter than the national average, and adjacent houses will soak up the extra amounts being exported before it adversely affects the substation.

More likely, it's that UKPN is prepared to sail closer to the wind.
It's commercially profitable to do so.

Provided a DNO meets the RIIO Agreement targets set by Ofgem, they're not required to upgrade the capacity of cabling or transformers.
Nor is there any data collected which could demonstrate the losses due to phase imbalance at regional levels.

Occasionally they'll get their fingers burned, such as the outage due to a transformer catching fire at North Hyde BSP on 21st March 2025.
Suddenly that's big news because it supplies Terminals 1, 2 and 3 at Heathrow Airport.
The supply arrangement meant that a failure on one of the three possible cables/transformers would result in the loss of critical safety equipment.

Two previous occasions were ignored when tests on the transformer cooling system showed abnormal readings.

There was a lack of system resilience.

UKPN could equally well point out that the majority of the power required by Heathrow is supplied from the western side.
Those Feeds are the responsibility of SSE, and remained unaffected.

So was the problem really one for which UKPN could be held responsible?
Or is it the fault of Heathrow's Management who didn't buy-in off-grid generation/storage for the mission-critical equipment?

 SE England has a track record of approving utility supplies from companies who have low system resilence, lack of investment in infrastructure,
and a cavalier attitude to tackling waste and losses.

They seem to believe that all be OK because it's worked alright for the past couple of decades.

@bash First come first served, until the substation threshold is reached and then they only provide G98 limits, that’s what the ENW network engineer that did our G99 review told me. 

With a large heat pump load ( i vaguely recall it’s 32A) and battery I’m not sure I could fit an EV charger, even if I wanted to. I think the house fuse is about 100A and they must add some sort of safety factor to their calcs. 

@papahuhu I further understand that the DNO’s preference is to fit a maximum of 80 amp fuses. Regards, Toodles.

Posted by: @papahuhu

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until the substation threshold is reached and then they only provide G98 limits, that’s what the ENW network engineer that did our G99 review told me. 

That's poor science.

Transformers (and underground cables) are often under-specified wrt to present-day demand loadings.

They can continue to operate satisfactorily at increased temperature, provided that they also have time to cool down between max-demand peaks.

In most cases, transformer design is such that its reverse-power capacity is half that in the forwards direction.

But that's not the problem which commonly occurs due to excessive export from single-phase embedded generation.
Losses due to phase imbalance is the issue, and that occurs well before the max-power thresholds in either direction.

Posted by: @papahuhu

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I think the house fuse is about 100A and they must add some sort of safety factor to their calcs. 

Yes. The point at which the DNO would normally require the home-owner to accept a 3ph supply is when the dwelling is operating above 60A in a steady-state.

Although an electric shower would usually require 40A, that doesn't count because it only last a few minutes...
... depending on the composition of your household of course!

Nor would the use of power tools be counted towards the 60A threshold.

But EV chargers, heat-pumps, electric ovens and induction cookers do count of course.

Posted by: @toodles

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I further understand that the DNO’s preference is to fit a maximum of 80 amp fuses.

True. See this public announcement from 2023.

Posted by: @transparent

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…

Yes. The point at which the DNO would normally require the home-owner to accept a 3ph supply is when the dwelling is operating above 60A in a steady-state.

….

That’s an interesting bit of phrasing. Does that mean that, over 60A, the homeowner would be required to allow the DNO to install 3-phase (at the DNO’s expense) or that the homeowner could be obliged to pay (potentially £000s) for the DNO to do such an installation?

@toodles I think you are correct. I just popped to the garage and mine is 100A, don’t know why. When they were fitting my battery gateway to the meter tails my useless installer damaged the tabs that secure the fuse and I had to call the DNO to repair it. They didn’t try to downgrade it when they had the chance.

If I was on an 80A then I doubt I could ever fit a fast EV charger without an upgrade. But I’m very much not an electrician, I don’t touch anything that I can’t see nor thoroughly understand and can kill me. 

Posted by: @majordennisbloodnok

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Does that mean that, over 60A, the homeowner would be required to allow the DNO to install 3-phase (at the DNO’s expense) or that the homeowner could be obliged to pay (potentially £000s) for the DNO to do such an installation?

The answer will depend on the circumstances and by how much the steady-state demand exceeds 60A

DNOs are unlikely to be heavy-handed in their approach.
This isn't comparable to Energy Suppliers trying to install prepayment meters for households in debt.

If the household supply is provided by overhead wires, and if the nearest pole already has 3-phase available, then the costs are sufficiently small that the DNO might undertake this for a nominal fee.
In the case of a householder on the Priority Services Register, they may even undertake the work free of charge.

However, if there's substantial work involved to dig a trench, especially one which must cross the public highway, then this can be very expensive.

1: The householder will in any case have to bring in an electrician to fit additional consumer unit(s),
and then divide the appliances between the phases.

2: The Energy Supplier must be asked to install a 3-phase vector-sum smart meter.

3: The DNO might be willing to leave the household on single-phase if the householder proposes to install a storage battery in such a way that peak demand can be reduced.

DNO's are generally helpful and open to alternative strategies.
It's up to the householder to discuss the situation and try to be as flexible as possible.

Posted by: @papahuhu

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[...] had to call the DNO to repair it. They didn’t try to downgrade it when they had the chance.

That's unusual.

The ENA guidance is for 100A Service Fuses to be replaced with 80A whenever there is a need for a DNO to attend on site.

Posted by: @papahuhu

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If I was on an 80A then I doubt I could ever fit a fast EV charger without an upgrade.

That depends what you mean by a 'fast charger'.

It usually means a charger operating above 7½kW (32A trip),
for which the common solution is a 22kW 3-phase charger.

@transparent 

Yep, they didn’t even mention it. When I reported the damage they made a big fuss and treated it as a huge emergency, which I didn’t understand. They had been in and out within 3 hours of the call, perhaps this team only dealt with emergencies. The chap was very professional, I guess they have to be not to die working with the high voltage stuff, nothing like the normal jobbing spark.