[Mark I]

The charity-owned outdoor centre where I'm a volunteer desperately needs a 3-phase power upgrade, but cannot afford the quoted cost and this proposal would be less than zero help for that. Our challenge is that we have a single-phase pole mounted transformer feeding just our site (plus a weather monitoring station a quarter of a mile further along the access track). To get 3-phase power we'd have to pay Northern Powergrid to replace their transformer, so the net cost to us would be in the high 5-figures, far more than what's left of our reserves for all purposes, after Covid ate the lot a few years back.

(There's a lovely modern 11 kV 3-phase-capable power line as far as the transformer, only about 20 metres away, which is good. Unfortunately the decrepit 1960s transformer was replaced with another single-phase job relatively recently, so no hope of asking for a 3-phase upgrade when it dies.)

 

[Mark I]

One huge good feature if these OBELISC things are designed well should be to remove some of the need for synchronisation of all the works needed for power upgrades. First, get a 3-phase box installed at the boundary, with its 3-phase meter, and just one phase connected in to the old 1-phase power cable running into the house. Second, get the ground, building and electrical work done for whatever improvements are needed, without having to call the DNO to keep pulling and replacing their fuse and re-sealing equipment. That supposes that the kit in the box will include a 3-phase isolator switch of which the output can legally be connected and re-connected by a regular electrician.

 

[dirk362]

Taking a step back, I challenge the logic of why this is being proposed.
Today, most households have single-phase and can have up to 100A supply, albeit some regions now seem to try to limit to 80A.

My 3-bedroom link-detached house is all electric and has EV, heat pump, induction hob, etc. And all works perfectly fine on my 100A single-phase supply, accepting it was all done as retrofit and I made a conscious decision to dial-down the power on the induction hob to 2kW as I wasn't confident in the cable run to the fuse box - which incidentally is high up on the wall just inside the front door.

Moving to three-phase to physically split high load items seems a weird decision to me unless there is some way in which these might be limited or controlled, or unless they're going to allow more amps per phase such that overall household load can be more than 100A.

That said, any house with existing cabling that can cope with up to 100A on single-phase surely doesn't need this unless it's a larger property. It isn't like all high-powered usage will be concurrent for many hours at a time, so I'm not sure you'll see houses drawing more than say 60A even under heavy load in general day-to-day usage. That is fine for what we have now.

The linked article at National Grid states the following objectives

• Develop a novel solution for upgrading customers to a three-phase supply, so they can adopt LCTs to achieve net zero
• Develop a new three phase connection point which can be installed at the boundary edge of domestic properties
• Deliver a solution which key stakeholders and end users will accept to be installed at the boundary edge of domestic properties
• Design a cost-effective solution which reduces the cost and disruption of upgrading customers to a three-phase supply
• Increase the capacity of LV networks to connect large volumes of low carbon technologies by balancing load across all three phases

Meaning the overall reason this has been instigated is really the first point, namely, to supply Low Carbon Technology within households.
To me, unless you have a large property, that seems eminently doable with the current single-phase solution we have today.

If this is going to be in effect paid for by everyone, with some of the costs allocated across utility billing within the Service Charge element, then I'm massively against this. Why should everyone subsidise the work for those that do this, who are more likely to be better off people in the first place? The DNO's are not going to do this for free, as this is a serious amount of engineering work per household supply, so those costs have to go somewhere, and should go to those asking for this to be done, not to everyone.

 

[Mark I]

Today, most households have single-phase and can have up to 100A supply, albeit some regions now seem to try to limit to 80A.

More precisely, most households have a 15 kVA supply (i.e. about 63 A continuous since the nominal 230 V power is usually close to 240 V), with an 80 A or 100 A fuse to protect against supply cable overload. That 100 A fuse is not a licence to use more than 63 A for an hour or more, just a cut-off with a decent margin for short-term overload without needing lots of emergency callouts to replace the fuse in the service head. Some domestic supplies have a lower than 15 kVA rating, but I don't remember the details (need @Jeremy Harris for those).

 

[srichards]

I'd think uprating the standard single phase to 120 amp and having better supply cabling would be cheaper.

How does using all 3 phases to a property instead of having single phases to a group of 3 and balancing that improve things? It just sounds like a lot more cable as you have 3 runs instead of one fat one.

 

[dirk362]

More precisely, most households have a 15 kVA supply (i.e. about 63 A continuous since the nominal 230 V power is usually close to 240 V), with an 80 A or 100 A fuse to protect against supply cable overload.

Yes, agreed.
My point was, as a converted household to electric only, I struggle to push a really high load onto the supply in the likes of free electricity sessions. If I charge the EV (32A max), run ASHP for DHW tank (16A max at start, tends to be ~3A in general usage), put say the tumble dryer on (16A max, or more realistically 10A in operation), and turn on the kettle (10A), I can perhaps get to a theoretical load of 74A, but in actual fact when I did all this once last year it was only around 60A in actual real world usage after the first 5 minutes or so.

Yes, I accept it is perfectly possible to push more than the cable/supply is designed to accommodate, and that this can and would occur with simultaneous high-load items starting at the same time, going over the 63A threshold. But from a continuous usage model, it is actually surprisingly difficult to use more than 63A all the time.

All my waffle said, my house usage profile is just for me, and I can see that the 63A continuous load threshold could and would be exceeded on larger properties or households with more people in them, all doing different things. Or with more than 1 EV for example.

In my humble opinion, I can see the argument for moving to three-phase for large 3-bedroom and bigger homes, so as not to make the electrical supply a limiting factor in the adoption of Low Carbon Technologies.

On the point of installing these boxes on the boundary of the property, many council planning boards would be against this, as the 'modern' design for housing is to ensure the front boundary is open and does not have fencing or bushes. Putting one at the boundary would be an eyesore in the eyes of the planning department.

 

[Mark I]

I'd think uprating the standard single phase to 120 amp and having better supply cabling would be cheaper.

How does using all 3 phases to a property instead of having single phases to a group of 3 and balancing that improve things? It just sounds like a lot more cable as you have 3 runs instead of one fat one.

They are thinking of the household with 3 EV charge points, charging on all of them overnight ready for going off to work next morning, next door to the same-sized house with a retired person living in it, who uses one car and rarely charges it at all. One's drawing 96 amps and the other about 1 amp overnight. Far better to have the three charge points on a phase each, or even three 3-phase charge points.

Home EV charging is especially lumpy, being big loads but not necessarily at the same time as the neighbours (unlike heating, for example, where every house gets the cold weather at the same time).

 

[electric_dreams]

4. More smart metering problems, the electric meter is now at the bottom of the garden, the gas meter which talks to it is at the house, the IHD is somewhere in the house. You'd expect there will be more local comms problems because the signal strength will be worse.

My electricity meter is at the back, the gas is at the front - I already have communication problems. If the electricity meter was at the bottom of the garden I don't think I'd get any data at all!

 

[TakeNobodysWordForIt]

They are thinking of the household with 3 EV charge points, charging on all of them overnight ready for going off to work next morning, next door to the same-sized house with a retired person living in it, who uses one car and rarely charges it at all. One's drawing 96 amps and the other about 1 amp overnight. Far better to have the three charge points on a phase each, or even three 3-phase charge points.

Home EV charging is especially lumpy, being big loads but not necessarily at the same time as the neighbours (unlike heating, for example, where every house gets the cold weather at the same time).

Not sure what is better. One phase each over three houses or three phases to each house and they all have multiple chargers, accidentally plugging into the same phase by chance. It's likely to be rare but given enough installations it will happen.

 

[Pmholling]

My electricity meter is at the back, the gas is at the front - I already have communication problems. If the electricity meter was at the bottom of the garden I don't think I'd get any data at all!

As in you have HAN or WAN communication issues? On the latter moving the hub to another location on the property might help or hinder. On the former, the premise in this setup is that 3-phase electricity replaces both the single phase connection and the gas connection, no worries about HAN comms issues.

 

[GavJ]

So ditch all the existing cabling and run new by digging up hundreds of rear gardens and/or access roads.

Not convinced they will be considering such disruption. I suspect we would have one of these in the front and only those who are doing major work on their house will make use of more than a single phase

Well they won't be digging up the garden, you will when you are ready. The cabling after DNO cut off is yours to sort out.

Obviously as more people get smart meters they can see loads values per phase and upgrade roads where there are likely issues. In other places where there isn't much variation then there won't be much need to do this work.
Some of this work might just be part of the natural upgrade cycle.

 

[GavJ]

It's free in the sense that smart meters are free. I.e. everybody pays for this through their energy bills over a long period of time. The only money in the system is either a levy on energy suppliers -> energy bills or general taxation and I don't think it will be the latter.

Yes free to me, paid for from the greater good! 😁
We all pay into funds that we don't use, it will just be nice to get something out of the system at some point.

 

[blueacid]

I'd think uprating the standard single phase to 120 amp and having better supply cabling would be cheaper.

How does using all 3 phases to a property instead of having single phases to a group of 3 and balancing that improve things? It just sounds like a lot more cable as you have 3 runs instead of one fat one.

Not sure what is better. One phase each over three houses or three phases to each house and they all have multiple chargers, accidentally plugging into the same phase by chance. It's likely to be rare but given enough installations it will happen.

It's largely to do with neutral current and balancing the phases.
The grid largely wants all three phases to be balanced. So if your household needs 60 amps, it's far better for the grid for them to see that as 3x20A rather than 1x60A. The risk of one house being a heavy user (2xEVs to charge, electric hob, heat pump) and others on the other phases being diesel cars, gas boilers, and gas hobs is probably pretty high. I suppose it also helps for new builds as well; if they get 3x40A then that's good for a 3x16A car charger (11kW not 7kW charging - whoop!), and a 3-phase induction hob, and 3-phase heat pump. With lower currents on each phase, that means thinner wires, and generally nicer setup all around..!

 

[Scubakid]

This all sounds OK but if you take a household (like me) with a heat pump, EV, solar and batteries getting this all to work efficiently would mean swapping out my current inverters for 3 phase ones so as to maintain the efficiency of the system to only use grid power when there was no solar or battery power available. That said if I knew this was certain to happen and at no cost, then if any of my existing equipment became end of life or failed then I would replace with new 3 phase compatible parts.

John

 

[BornAgainEcoWarrior]

while they are at it they can stick a small battery in each box. The distributed storage would enable them to shift loads and buffer high demand eliminating the need to upgrade wiring and reducing the need for system balancing and curtailment. It could end the need for peak generation and make the system immensely robust.

 

[blueacid]

Oh it's worth pointing out that at the moment, 3 phase smart meters use net metering.

So let's suppose you wire a solar inverter to Phase 1, your house loads to phase 2, and leave phase 3 unconnected. If you are exporting 1kW on phase 1 but importing 1.5kW on phase 2, the meter will consider this to be a 500w import.

That's, at least, how things are today.

 

[TonyH]

Don't most houses these days already have the meter cabinet on the outside wall (rather than inside)

I actually like the idea postulated by the presenter that 3 phase indoors creates more heat... I'm all for some free heat then I don't need to run the central heating as long.

Meanwhile, putting the meter box on the property boundary is just asking for trouble when your local refuse collector/amazon/supermarket delivery company drives into it. Not sure how it would work for a house with a covenant (like mine) that prohibits erecting things on the property boundary (I'm not even allowed a fence)

It would also make gas smart meters even less smart (as they connect wirelessly to your electricity meter to report consumption) My gas smart meter already very rarely works as the meters are too far apart, putting the electricity meter on the boundary is even further away.

 

[BeesKnees]

Well they won't be digging up the garden, you will when you are ready. The cabling after DNO cut off is yours to sort out.

I wasn't referring to my garden, I was referring to all the gardens and small access roads the grid would have to go through to reach my back garden .

 

[Brian G]

Seems to me that there is an issue that the DNO faces with the demographics of households. There are more single person households than there has been of old. Where you have a family of 4 or 5 and the younger ones become drivers, you have an issue with more than one vehicle to charge. That might be manageable with one charger but much more manageable with 2 or more chargers and one of those chargers might be 3 phase. There is a bit of a gap in battery size between those happy to live with 50 kWh batteries which tend to be the smallest now acceptable (excepting city type EVs) and those with 70 kWh and over where 3 phase charging is very desirable and is usually available on the car's on board charger. Having one household with a heat pump and 2 chargers restricted by CT clamps is very likely to be pulling the full 16 kW for 7 hours or more over night. And that will screw the local system. It is the random mix of bigger households with the need to pull all 16 kW and the neighbours who don't that will cause the issue. I live in a close of 8 houses, nos 1,2,6,7,8 are 2 person households, no 3 is a one person household and 4 and 5 are 5 person households. Only we at No1 have a heat pump and an EV. Nos 4 and 5 have older kids with cars but no electric as yet. We and No.4 and No.6 are on the yellow phase. The red phase has a widow lady and a 2 person household who are away frequently undertaking family duties, child minding and granny assistance. The phases will never be in balance and therein lies the rub. We can happily pull 11 kW when the car is charging and the heat pump is working hard add the dishwasher and that peaks at 14 kW, 6 of the houses have gas ch and one oil. In 5 years time all the 8 houses are likely to have one EV and some might have 2. I suspect 2 of the houses will be due for a new boiler at some point and they might likely go for heat pumps.
A few years ago we had a flickering of lights and lo SSE turned up and dug up the verge to repair the cable and there was a muttering that they had laid some cheap German shit in 1984 when the houses were built and pressure from vans driving on the grass had cracked the insulation, all 8 houses were getting intermittent 3 phase down their one pair of wires...!
So I can see why 3 phase distribution is being considered. It will be useful to locate it on the verge where it can be easily divided to support EV charging at a property and maybe the power companies will be asking that car makers install 3 phase on board chargers in cars for the UK market and not just for the EU. It isn't that we all need 3 phase or that households will generally exceed 16 kW load but the vagaries of what is drawn via each phase.

 

[TonyH]

maybe the power companies will be asking that car makers install 3 phase on board chargers in cars for the UK market

Aren't the chargers built into most cars capable of taking a range of power inputs - from 240v AC at 10A all the way to 800v DC up to about 400A