Green Building Forum - What are the parameters on the grid that prevent feed-in Tue, 19 Dec 2023 08:18:26 +0000 http://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 What are the parameters on the grid that prevent feed-in http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17626&Focus=298489#Comment_298489 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17626&Focus=298489#Comment_298489 Mon, 31 Oct 2022 13:10:41 +0000 Peter_in_Hungary how far up the grid will problems be seen - from the consumer to the first transformer or further back all the way to the power station?
What is the upgrade(s) typically needed to enable feed-in?]]> What are the parameters on the grid that prevent feed-in http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17626&Focus=298494#Comment_298494 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17626&Focus=298494#Comment_298494 Mon, 31 Oct 2022 15:17:34 +0000 djh What are the parameters on the grid that prevent feed-in http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17626&Focus=298496#Comment_298496 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17626&Focus=298496#Comment_298496 Mon, 31 Oct 2022 15:56:54 +0000 owlman What are the parameters on the grid that prevent feed-in http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17626&Focus=298497#Comment_298497 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17626&Focus=298497#Comment_298497 Mon, 31 Oct 2022 16:29:50 +0000 djh Posted By: owlmanAs I understand it, it's also the number of other users in the immediate area who use up the power before it gets to the first substation.Well, the number of other consumers only matters in so far as they affect the voltage and whether it breaches limits. Or less likely, the current rating of the local system.]]> What are the parameters on the grid that prevent feed-in http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17626&Focus=298501#Comment_298501 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17626&Focus=298501#Comment_298501 Mon, 31 Oct 2022 19:58:49 +0000 Peter_in_Hungary What needs to change on the grid so that this over voltage is not a problem? Can (will) the excess power be absorbed by the grid through the low to medium voltage transformer and from there all the way back to the power station that reduces output to compensate. Otherwise how is it managed?]]> What are the parameters on the grid that prevent feed-in http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17626&Focus=298502#Comment_298502 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17626&Focus=298502#Comment_298502 Mon, 31 Oct 2022 20:14:34 +0000 djh Posted By: Peter_in_HungaryI am thinking of the low voltage local network where several domestic PV systems are feeding in at a level that exceeds the local demand which will cause a voltage rise (yes?)Yes.
What needs to change on the grid so that this over voltage is not a problem? Can (will) the excess power be absorbed by the grid through the low to medium voltage transformer and from there all the way back to the power station that reduces output to compensate.
Each local transformer is set so it delivers a legal voltage range under normal conditions. If they build another house or two and add them to the circuit they may need to increase the transformer setting to deliver slightly more voltage so it stays in the legal range at the houses. PV complicates things, because it pushes the voltage up and tests the other, high end of the range. So if there's a lot of PV they may need to turn the transformer down. But then it gets dark at night etc etc. There's only so much they can do. So they may need to split a circuit and put a new transformer in, and/or beef up the circuits so there is less loss in them. Ultimately, depending on how much generation is connected and the topology of the local grid, other parts upstream of the local bits may need upgrading as well. But it's all real work involving people in fluorescent jackets, not pushing buttons in offices. And yes, ultimately it results in one or more power stations reducing their output a bit.]]> What are the parameters on the grid that prevent feed-in http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17626&Focus=298503#Comment_298503 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17626&Focus=298503#Comment_298503 Mon, 31 Oct 2022 20:19:03 +0000 owlman Posted By: Peter_in_HungaryI am thinking of the low voltage local network where several domestic PV systems are feeding in at a level that exceeds the local demand which will cause a voltage rise (yes?)

Isn't that the job of the DNO; to ensure that doesn't happen?]]> What are the parameters on the grid that prevent feed-in http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17626&Focus=298507#Comment_298507 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17626&Focus=298507#Comment_298507 Mon, 31 Oct 2022 20:59:44 +0000 philedge Posted By: Peter_in_HungaryOtherwise how is it managed?

First off, if everyone plays by the rules and submits a G98 notification/G99 application, the DNO will know exactly how of each type of generation there is on any particular section. They can then increase transformer size if needed or retap existing transformers to keep voltages within statutory limits- 230vac +10%/-6%. AFAIK theres a range of supply logging goes on in sub stations and the DNO can see if voltages are fluctuating in unexpected ways, so if a whole street installs PV without notifying the DNO, the DNO will know they've done it as the local substation voltage will rise every time the sun shines.
I read somewhere of somone saying their DNO retapped their local transformer seasonally to lower the local voltage in the summer when there was a load of PV pushing it up.]]> What are the parameters on the grid that prevent feed-in http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17626&Focus=298523#Comment_298523 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17626&Focus=298523#Comment_298523 Tue, 01 Nov 2022 10:42:15 +0000 bhommels Posted By: philedge
I read somewhere of somone saying their DNO retapped their local transformer seasonally to lower the local voltage in the summer when there was a load of PV pushing it up.
I guess it will come down to putting in some power electronics to make retapping a 'from the computer console' operation instead of a 'hi viz jackets' one.]]> What are the parameters on the grid that prevent feed-in http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17626&Focus=298525#Comment_298525 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17626&Focus=298525#Comment_298525 Tue, 01 Nov 2022 11:15:18 +0000 djh Posted By: philedgeI read somewhere of somone saying their DNO retapped their local transformer seasonally to lower the local voltage in the summer when there was a load of PV pushing it up.I don't quite understand that. PV doesn't push the voltage up at night, so at night conditions are the same as if there was no PV. Perhaps there was a large electric space heating demand that needed the voltage to be pushed up in winter?

FWIW, More than you, or I, ever wanted to know about transformer taps https://electrical-engineering-portal.com/transformer-voltage-regulation

And for no particular reason, similar for forecasting https://otexts.com/fpp2/]]> What are the parameters on the grid that prevent feed-in http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17626&Focus=298533#Comment_298533 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17626&Focus=298533#Comment_298533 Tue, 01 Nov 2022 14:17:12 +0000 philedge Posted By: djhI don't quite understand that. PV doesn't push the voltage up at night, so at night conditions are the same as if there was no PV.

I think the idea is that by dropping the voltage the daytime PV doesnt push the voltage over 253v and at night they would run a slightly lower voltage than optimum.]]> What are the parameters on the grid that prevent feed-in http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17626&Focus=298534#Comment_298534 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17626&Focus=298534#Comment_298534 Tue, 01 Nov 2022 15:04:57 +0000 djh Posted By: philedge
Posted By: djhI don't quite understand that. PV doesn't push the voltage up at night, so at night conditions are the same as if there was no PV.


I think the idea is that by dropping the voltage the daytime PV doesnt push the voltage over 253v and at night they would run a slightly lower voltage than optimum.Yes, but then there'd be no need to adjust it upwards in winter?]]> What are the parameters on the grid that prevent feed-in http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17626&Focus=298535#Comment_298535 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17626&Focus=298535#Comment_298535 Tue, 01 Nov 2022 16:23:34 +0000 philedge Posted By: djhYes, but then there'd be no need to adjust it upwards in winter?

Wind it back up when PV tails off to get the most power down the wires when you need it most in the winter, AFAIK]]> What are the parameters on the grid that prevent feed-in http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17626&Focus=298542#Comment_298542 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17626&Focus=298542#Comment_298542 Wed, 02 Nov 2022 12:48:45 +0000 WillInAberdeen

For example, with no loads, our smart meter reports 229.7V, but when I turned on some heaters, the current went up by 19.4A and the voltage reduced by 5.8V. So the apparent impedance of our supply is 5.8/19.4 = 0.3 Ω .

If I applied to add say 15kW of PV, my voltage would go up to 250V which would be within limits, so the DNO could approve it. It would be my problem if the extra impedance across my home installation pushed up the voltage to trip my inverter.

By repeating this at different times when my neighbours are using more/less power, the DNO can work out how much of the supply impedance is on wires that I share with neighbours, and whether my PV would mess up the voltages at their supplies. They could consider if my export is at the same time as the neighbours, and whether they might want to reserve capacity to increase the substation voltage in future once we all get EV chargers.

(Edit to add: exporting lots of power will pull down the voltage of the Neutral conductor, as well as increasing the voltage of the phase conductor. There are various permutations of how closely Neutral is coupled to Earth. IDK if the 253V legal voltage limit is measured relative to Earth or to Neutral, that could affect the answer a bit. I note the meter doesn't have an earth connection.)]]>