@transparent Thank you for the great explanation, and for the exchanges today - really appreciate your help in gaining a better understanding of the issues involved.

It's frustrating to want to be more self sufficient / greener, and to be prevented from doing so. For others benefit, our property is located right next to the substation. The 3 closest properties to the substation (ours included) all had ASHP/solar installs in the summer, and one had a battery install too, although each would have been G98 (3.68kW). I guess part of the problem is we are all exporting at the same time as we all experience the same sunny periods, and if we are all exporting, there is no one to consume it. Am I right to infer from your explanation that properties further away from the substation would not consume our export?

We were hoping to add a further 3.56kWp (giving 7.2kWp total) plus battery storage which would have roughly covered our annual consumption. G99 application is in (courtesy of the installer), but it doesn't sound promising. If they won't grant more than the 3.68kW we already have on G98 (effectively denying the application), it looks like we will be asking for our deposit back. We should know in a few weeks.

@transparent Are you able to share information about our substation (either here or privately), including number of properties connected, and what solar/batteries/ASHPs etc may be installed in the locality?

@old_scientist I am similarly frustrated. I am in a different situation in that my property is furthest from my local substation so my inverters will have a lower mains supply voltage to overcome when exporting to my neighbours. However, if the transformer taps in the substation have been configured for a particular load from the houses connected then I can imagine that any reduction in power output from the substation, as a result of me supplying power to my neighbours from the other end of the supply cable, will result in a higher supply voltage for those neighbours nearer the substation due to there being a lower voltage drop from the substation. It’s now easy to see why the difference between day and night load on a substation becomes a problem. Add the need to balance loads on the 3 phases and we can then appreciate the problems the DNO has with the ‘last mile’.

Posted by: @old_scientist

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Are you able to share information about our substation

Sure. Here 'tis

• Transformer size: 315kVA, with four Feeds
• Daytime max. demand: 145kVA
• Night-time max. demand: 89kVA
• Connected properties: 123
• EV chargers: 3 (assumed to be 7½kW each)
• Heat pumps: 6
• Solar generation: 41 properties
• Storage batteries: none

Let's remember that these consumer statistics are based on G83/98/99 and LCT applications which are correctly made to NGED.

Where householders or installers have not sought permission, then the data will be incorrect.

Whenever there are obvious anomalies, NGED has a 'sniffer' which can be deployed.
That might be used, for example, if underground cables or the transformer itself are getting hot.

Posted by: @transparent

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Posted by: @old_scientist

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Are you able to share information about our substation

Sure. Here 'tis

• Transformer size: 315kVA, with four Feeds
• Daytime max. demand: 145kVA
• Night-time max. demand: 89kVA
• Connected properties: 123
• EV chargers: 3 (assumed to be 7½kW each)
• Heat pumps: 6
• Solar generation: 41 properties
• Storage batteries: none

 

Let's remember that these consumer statistics are based on G83/98/99 and LCT applications which are correctly made to NGED.

Where householders or installers have not sought permission, then the data will be incorrect.

Whenever there are obvious anomalies, NGED has a 'sniffer' which can be deployed.
That might be used, for example, if underground cables or the transformer itself are getting hot.

Thank you!

The solar uptake seems high at 33.3%.

The numbers may well be higher, as I know at least one of my neighbours has battery storage, which obviously has not been notified.

With respect to the original topic in this post, back in the summer I had a 12kW ASHP (permitted development) and 3.645kWp solar array with 3.0kW inverter (G98) installed under the ECO4 scheme.

Whilst the general installation was excellent, the paperwork and permissions were a little lacking. After all the works were completed, I chased up my solar installer for he MCS cert and DNO letter to register with my electricity provider for SEG. Eventually I gave up waiting on them and contacted NG directly. NG were brilliant, they informed me they had yet to be notified of the solar install, and advised me I could submit the details myself as I was familiar with the equipment that had been installed. NG issued the letter the next day by email, and I was able to register for SEG.

Next issue was my fuse. I was on a 60A fuse and wanted that upgraded to 80A which I understood NG would do free of charge, so I contacted them about that (as I understand it, the electrician probably should have assessed my demand and had the fuse updated before the installation). It then transpired they had not been notified of the ASHP installation either. Again, NG were extremely helpful in assisting me with the required paperwork, and a few days later an engineer phoned me to arrange a time to upgrade the fuse. He was on site for all of 10mins, electricity off, swapped the fuse, and back on again just in time to make us both a cup of tea. There was some discussion around our maximum demand (as we have 12kW ASHP, 9kW electric shower, 2.7kW+2.5kW double electric oven ...) and could theoretically pull over 80A if everything were on at the same time, but they were happy 80A would be OK. As mentioned previously, NG now have a policy of 80A max, see here:

https://www.nationalgrid.co.uk/downloads-view-reciteme/633928

One wonders how many installations there are out there that have occurred under various government schemes where the DNO has not been correctly notified. I've spoken with a few people lately who've had solar panels installed and had no idea they may be generating more electricity than they can consume, and can be paid for the exported excess under SEG.

Posted by: @old_scientist

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One wonders how many installations there are out there that have occurred under various government schemes where the DNO has not been correctly notified.

I agree.  I have my own doubts about the veracity of the data @transparent provided for my local substation.  I wonder where we'd be without the level of industry regulation we presently enjoy😱.

Posted by: @old_scientist

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One wonders how many installations there are out there that have occurred under various government schemes where the DNO has not been correctly notified. I've spoken with a few people lately who've had solar panels installed and had no idea they may be generating more electricity than they can consume, and can be paid for the exported excess under SEG.

I think there's a lot of homes where the DNO's records are incorrect...
... and that has a knock-on effect when the householder tries to 'do the right thing' and install a heat pump, for example.

But those of us in the general public are in a position where we can do something about it.

DNOs are very happy to receive information from us which adds to their knowledge of the LV network in particular (that's everything below 1000v).

Personally I'd be much happier to help people install storage batteries rather than attempt to earn income from the SEG.

The present system of tariffs and regulatory financial controls are not a good match for the way in which the grid actually works.
The costs of operating and maintaining the grid would be lower if the rules reflected 'good science'.

We shouldn't be relying on future income from exporting electricity in our RoI calculations.

That income stream can be swept away by a single change of policy from DESNZ or a Directive issued by Ofgem.

Adding in-house electricity storage

• reduces grid loading at times of peak demand
• reduces losses due to phase imbalance at the local substation
• adds resilience for both the household and the grid

@old_scientist and I are each waiting for the other one to start a new Topic which lays out the various different approaches to battery storage.

Any day now, one of us will have enough time to do so.