Large arrays / NC7 applications

maclek

Wondering if there are any updates on NC7 applications? I'm going to put in planning for a new build this month with 80 panels on an east / west roof, 32kwp to 40kwp I reckon.

I know @TerraSolis has this interesting post on their experience but that's a fairly unusual set-up!

@blobert seems to have been doing something similar to me, I wonder how they're getting on?

The esb says "The rollout of smart meters for 3 Phase customers will begin in 2025.  The deployment will initially focus on those 3 Phase customers who are on a standard 24-hour electricity tariff."

Do we have any idea what criteria are being considered when we roll the €1000 dice? Is it local transformer capacity? Does the amount of local solar panels affect things? In my case no one in the locality has any solar panels.

maclek

Also does anyone have any recommendations for installers who have experience with this?

10-10-20

What would you classify your residence as - rural, city/urban or regional town based? I'm asking as I guess that ESBn will treat each somewhat differently density the scope differs significantly due to localised density.

TerraSolis

https://www.boards.ie/discussion/2058344609/large-arrays-nc7-applications

"Do we have any idea what criteria are being considered when we roll the €1000 dice?"

Sure do!

1st thing they'll do is assess your cable connection between your meter box and transformer to a) estimate the length of the cable run and b) check the cable size to ensure it's got sufficient capacity to not screw the transformer with voltage rise.

If your connection is very old, it'll have smaller cabling that they currently like to put in and you're more likely to have an export limit applied to your NC7 to avoid voltage rise.

They then use a) and b) to make some X/R (reactance/resistance) calculations and adjustments in their assessment of your local connection point in assessing the transformer's limits.

Primarily, it all comes down to the local transformer. So there they're looking at thermal & harmonics limits.

In terms of nobody else in your locality having solar, that actually doesn't matter. ESBN confirmed to me in an email "ESB calculate the impact for each customer alone and rely on planning and compatibility limits in  the Dist. Code  to provide the necessary ‘headroom’ for other customers to be accommodated i.e. we exclude the other customer and also make a small correction for the actual X/R ratio."

Finally, recall that kWp won't matter - purely the kW / kVA ratings of your inverters. So you can pick inverter which allow significant DC oversizing if you want to achieve a large (DC) array with a higher chance of NC7 success (with as minimal or lean inverter capacity as is suitable).

As a reminder for folks looking to go the NC7 route, it's best to make your system up of more smaller inverters (e.g. 4X 4kVA inverters = 16kVA is better than 2X 8kVA inverters = 16 kVA) as this is far more favorable for the harmonics assessment. You also buy yourself some critical redundancy if one inverter were to go pop.

Hope this helps :)

10-10-20

https://www.boards.ie/discussion/comment/121964735#Comment_121964735

Fascinating overview there.

Given that we have previously heard that the NC7 is a blind submission from the perspective of the customer - was it ever implied that an assessment can be made in advance to understand the local power limitations and then size or design the inverter in advance so that the NC7 request would likely be successful? I mean to have a third-party obtain the local transformer data and run the numbers and come up with go/no-go on a variety of configurations, then submit an appropriately sized proposal?

slave1

https://www.boards.ie/discussion/2058344609/large-arrays-nc7-applications

Your local transformer MIC and MEC is available on an esbnetworks map, I don't have the shortcut to hand. At the very least when you see that you will see is there spare capacity to feed your build (likely but depends on location) and for you to feed back (very likely).

It's not in stone though, I was toying with a NC7 and increased feed but my transformer has no spare capacity for extra kva into my house, a casual conversation with Mr Esb and I was told I'd have to stiff a bill for transformer upgrades so I put it out of my head.

Lo and behold a new build went in last year to my transformer (heat pump/car charger etc) and the esb allowed them to take a feed as "they knew someone" in networks, typical Ireland

TerraSolis

https://www.boards.ie/discussion/comment/121965213#Comment_121965213

Yeah in fairness to ESBN, they obviously enjoyed my hack job attempt at doing just that considering the technical team came back to me with a detailed response.

Great question. It was never implied that an assessment could be made in advance so I would recommend people to do their best at that part themselves (IE is your local transformer seemingly busy with inverter connections already? How much kVA do you estimate is already connected? What does that leave available thermally speaking?).

However, once they'd calculated the limits, ESBN would've allowed me to alter the design offered me below what I was seeking and to meet that (so I could've adjusted the NC7 form with a new design without paying and starting all over again).

Say I applied for 16 kVA. If it was determined that I could've connected up to 12 kVA, they would've allowed me to proceed with that as the next best thing. Or you can pay the cost of the works to upgrade the connection to connect the original 16 kVA of course, but I bet that would sting the wallet like hell and take forever.

Maybe when I find myself with more time I'll set up an assessment service 🧐.

maclek

Maybe when I find myself with more time I'll set up an assessment service 🧐.

<Take my money.gif>

Here's what I reckon is the closest transformer from https://www.esbnetworks.ie/new-connections/generator-connections-group/availability-capacity-map

It's about 100m away as the crow flies, who knows how far actually.

Transformer configuration: 400 kVA :Kiosk Substation
Demand Firm Capacity: 400 kVA
Demand Capacity Available: ~250 kVA
Parent Available MVA: 0.6

(Slightly obfuscated for privacy)

I was looking at something like the Goodwe GW25K-ET but the point about redundancy makes sense. It goes for €15,500 with 32kwh of batteries. Once I actually get an expert involved they may tell me I'm bonkers!

the_amazing_raisin

https://www.boards.ie/discussion/comment/121965353#Comment_121965353

It is very good to know that ESBN seems to try and make the best out of the resources available to you

As in if you apply for 16kVA and your connection can't support this, they come back with the offer of a lower kVA or upgrading infrastructure (I agree, you'll want some deep pockets for that option) rather than just rejecting your application outright

the_amazing_raisin

https://www.boards.ie/discussion/comment/121966015#Comment_121966015

I remember there was some talk about how often that map gets updated, something like every 6 months

So it's possible someone already beat you to it

SD_DRACULA

How am I supposed to read this?

Loads of capacity left?

the_amazing_raisin

https://www.boards.ie/discussion/comment/121964735#Comment_121964735

I can see the logic of 2 smaller inverters vs 1 big one for redundancy, but I've never seen the argument of 4 much smaller inverters for harmonics

Is it really that big a deal, and have you any links where I could learn more?

My eventual mega system is probably going to be 2 inverters with either 8-10kVA each. Going for 4 inverters would be a bit more expensive so probably something I'd want to plan for

ELM327

That's on the demand side. You'd also need to look at the generation capacity tab

SD_DRACULA

https://www.boards.ie/discussion/comment/121966345#Comment_121966345

Also loads?

TerraSolis

https://www.boards.ie/discussion/comment/121966341#Comment_121966341

Sure. For example from the response that ESBN technical assessment department sent me:

"when there are multiple inverters the phase angles of each harmonic are random, so that the vector sum of the harmonics can be lower, as they tend to cancel each other out."

and

"the required SC level is adequate to ensure that the 6, 6 and 4kVA are within Harmonic standards (although for clarity a single 16kVA would not"

Which tracks logically if you think about it.

In terms of whether or not it is a big deal, having studied the standards DSOs are a bit 'extra' when it comes to managing harmonics as many of the applied standards are dated and apply to old noisy pieces of kit. However, harmonics are a big deal if you're looking for NC7 success!

For advanced reading material on harmonics assessment, I recommend you read the EREC G5 Standard available here: https://dcode.org.uk/assets/uploads/ENA_EREC_G5_Issue_5__2020_.pdf

TerraSolis

https://www.boards.ie/discussion/comment/121966015#Comment_121966015

What's your current MIC?

I would strongly urge you to break that 25kVA into more like 5*5kVA paralleled. With the right kit they can still all share the same battery bank.

blobert

https://www.boards.ie/discussion/2058344609/large-arrays-nc7-applications

Hello,

Just to say I got the NC7 approved (it took a while and a bit of prompting) have a 3 phase meter running since last year and am about to order the equipment from China with an Irish installer lined up to install.

This line worries me "The rollout of smart meters for 3 Phase customers will begin in 2025.  The deployment will initially focus on those 3 Phase customers who are on a standard 24-hour electricity tariff. "

It was reading as starting in end 2023 last year I thought!

I'm planning to have about 30-40kw of panels, about 60kwh of batteries and a lot of this is based on being able to charge at cheap night rates, run the house on this and get paid higher rate for essentially exporting all the PV I generate.

If I'm only able to operate on deemed export it will make the payback period a lot slower.

Am I right in saying you only get 35% of your calculated total export amount this way as opposed to 100% if I were exporting it all?

ELM327

https://www.boards.ie/discussion/comment/121970270#Comment_121970270

Yup, thats right

Benefits those (like me) who export nearly 0 but punishes those who do export. Once my dumb/clever day night meter is exchanged for a smart/stupid RM108 meter I'll be investigating doing a change to NC7 myself. As it stands, it doesnt pay me to do it.

blobert

Thanks for that, I wonder if there's any way to prompt a 3 phase smart meter to get it faster.

Do we know what make/model smart meter they will be using?

randombar

So I received my NC7 connection letter back.

They're only offering me 8kVA instead of the 6kVA I currently have, no reason why or anything?

Not even sure what the next steps are?

10-10-20

https://www.boards.ie/discussion/comment/122035231#Comment_122035231

Akin to what @TerraSolis mentioned, I'd recommend trying to engage and have a discussion with their technical team/engineers via email and see if they would pass on any of the limitations around why you're stuck at 8kVA when you were hoping for more. You may find that there are plans to upgrade the local substation, but it would then be interesting to know whether you would have to reapply again for another upgrade if that were to happen…

https://www.boards.ie/discussion/comment/121965353#Comment_121965353

10-10-20

https://www.boards.ie/discussion/comment/122035231#Comment_122035231

Oh and would you be willing to tell us whether you are rural, city/urban or regional-town based? It's just so that we know the rough profile of the account.

graememk

https://www.boards.ie/discussion/comment/122035231#Comment_122035231

Any mention of export limiting?

randombar

https://www.boards.ie/discussion/comment/122035384#Comment_122035384

Rural. Local substation.

That's what is in the letter back

Rang networks and local crowd hopefully back in 2 to 3 days.

slave1

There seems to be a pretty consistent "we will sell you more but you cant export (much) past NC6" approach.

They seem to be restricting you to a ~8kW inverter too rather than a larger one with export limiting

10-10-20

https://www.boards.ie/discussion/comment/122038631#Comment_122038631

I would have thought that the two would have to match - MEC and inverter capacity. Have you seen otherwise?

idc

One of the benefits of NC7 though is export limitation, hence inverter could be higher assuming you have an acceptable export limitation scheme! Guessing whatever export limitation the inverter most likely has built in is not acceptable by ESBN!

10-10-20

Actually - just found this document:

https://www.esbnetworks.ie/docs/default-source/publications/conditions-governing-connection-operation-els

Page 23 has a good worked example and discusses much of what we are talking about.

slave1

https://www.boards.ie/discussion/comment/122038953#Comment_122038953

agreed but randombar has had inverter size restricted and no export limitation therefore allowed, would be better to have a 16kW (or dual 8kW) inverters which would be of great benefit outside peak production times and then have export limitation, this will also also say 16kW instant production capability with 8kW to grid, some to home, some to batteries, some to hot water, some to EV

10-10-20

https://www.boards.ie/discussion/comment/122039078#Comment_122039078

Wondering aloud, maybe there is an allowance for export limiting controllers under NC7? That could open up the possibilities of over-sizing both the inverter and the solar.

idc

@randombar out of curiosity is NC7 similar to NC6 and you list inverters to be connected? If so did you list 1 or 2 8kW inverters or a single 16kW inverter?
Maybe the solution would be to go back and add in whatever ESBN deems an acceptable Export Limitation System (ELS) ? You've been told max allowed is 8 and that may be likely due to constraints in document @10-10-20 found. So if you modified your system to include acceptable ELS would give you your 16kW BUT there may be no point doing that if your plan all along was to export the majority of your 16 kW !

randombar

https://www.boards.ie/discussion/comment/122039166#Comment_122039166

Solar company submitted on my behalf, I think they stated the 2 x 6kw inverters (only looked for 12kw NC7).

I'm very confused by the thermal capacity though.

Technically every house in the area could have up to 5kw of solar. 90% have none (I know all the neighbours) so rather than 3 houses have 15kw why can't 1 house have 12?

TerraSolis

I bet this is harmonics related… I was initially offered 7kVa MEC due to harmonics. Once I escalated, I got passed from a nice but slightly clueless grad hire to the boss man who re-did the harmonics analysis and showed that I could go ahead.

10-10-20

https://www.boards.ie/discussion/comment/122039258#Comment_122039258

That's the thing that we are all wondering. The specific question back to ESBn is "what is the limiting factor in the decision to restrict me to 8kVA?" We're thinking that it's either that thermal thing (from that document: "…because the most onerous constraint is thermal capacity...") or the harmonics.

randombar

https://www.boards.ie/discussion/comment/122039281#Comment_122039281

Is there anything I'd need in relation to harmonics questions before they call? Tech docs for inverters I'm guessing but how do they calculate?

TerraSolis

https://www.boards.ie/discussion/comment/122039364#Comment_122039364

Yes - you need certified harmonics data for the inverters in question (or they make really exaggerated worst-case scenario assumptions.) What inverters are you proposing? If you give me detailed model specs, I can see if I can find the right docs in the G99 database for you.

randombar

https://www.boards.ie/discussion/comment/122039391#Comment_122039391

2 x Solaredge SE6000H Screenless.

Installer was back onto his networks contact and apparently it's harmonics all right, that I've to argue my case.

There's two houses down my laneway fed off a three phase line, hard to see how the harmonics are bad?

10-10-20

Alright, making progress!

TerraSolis

SOETC_00164_190606024109.pdf

@randombar type tested data up to the 40th harmonic for the SE6000H attached. You'll be able to get this across the line, but you'll have to argue. They have assumed that your inverter exhibits the maximum harmonics allowable to comply with EN61000-3-12. You can now show that the inverter exhibits much lower harmonics as certified by the type test attached. They can now use this info to reevaluate harmonic limits.

randombar

https://www.boards.ie/discussion/comment/122039987#Comment_122039987

brilliant stuff. I’ll have plenty of ammo for call on Monday.

TerraSolis

https://www.boards.ie/discussion/comment/122040902#Comment_122040902

Any luck ?

randombar

https://www.boards.ie/discussion/comment/122095460#Comment_122095460

Guy rang me this evening about it actually, seemed like a sound guy, going to call out Tues, sent on the pdf and explained that I have a 16kva MIC, seemed open to investigate further and did explain this is all very new for them.

He was wondering if the transformer was the reason for the low MEC but I don't think he was aware of the 16kva. I'd say he hasn't looked at the case at all yet really and is only starting the investigation.

TerraSolis

"seemed open to investigate further" - That's the stuff. They'll sort you out as best they can now I'm sure.

randombar

https://www.boards.ie/discussion/comment/122099334#Comment_122099334

Investigations proved to be slower than I thought.

I'll go back to SolarEdge now for that information but I'll need to figure out what xx is now so I can get the MEC of 12.

============================================================================

The Harmonics data on it’s own as provided is not used in the calculator for Mini Generation. Therefore what’s provided would not allow for a higher MEC value.

What we need from the Manufacturers as per EN61000-3-12 is the following to assess this differently:

Some devices may produce lower levels of harmonic currents and hence lower voltage distortion, so that their kVA installed limit (MEC) could be higher.

Please see second paragraph below. Can you please engage with the manufacturer of the equipment to confirm the values denoted by ‘xx’ in this paragraph

TerraSolis

https://www.boards.ie/discussion/comment/122205469#Comment_122205469

The paragraph/screenshot isn't loading there. What's xx that they're looking for?

10-10-20

https://www.boards.ie/discussion/comment/122205469#Comment_122205469

Yeah, you linked to your gmail rather than the intended document.

randombar

https://www.boards.ie/discussion/comment/122205911#Comment_122205911

apologies

TerraSolis

https://www.boards.ie/discussion/comment/122206156#Comment_122206156

This again… What ESBN aren't accounting for here is that manufacturer's don't test for IEC 61000-3-12 compliance down to lower Ssc values, so ESBN's policy here isn't sensible. IEC 61000-3-12 is an old standard that is isn't fit for purpose when it comes to modern inverters and distributed gen.

In the UK, the recognize it and have developed a new standard called EREC G5. EREC G5 was developed by the Energy Networks Association and ESBN are actually a member. G5 doesn't require further manufacturer data and instead makes a calculation based off the inverter size.

I raised these points during debate around my own assessment and never had to provide further manufacturer's data. I would argue the case and request assessment under the G5 standard.

randombar

what figures do they use to test off g5 and what’s the equivalent equation?

TerraSolis

ENA_EREC_G5_Issue_5__2020_.pdf

See pages 45-47 of EREC G5. Pretty straight forward. They just need the power rating

randombar

The latest:

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So to progress any application they have for accepting their Inverter we need a Type Test confirming that it conforms to EN 50549 – conforming to EN 50539 automatically means that it meets EN 61000 requirements, and that the Rsce to be used is 33.

IF they want to have a lower Rsce used then they need to get a Type Test to EN 61000-3-12 (which goes up to 50kVA 3 phase) showing that the equipment has been validated at a lower Rsce, or that it is within limits at a particular short circuit level (Psc). These calculations are done by the Type Test Laboratory and need to come from the Type Test Lab.

However, every Inverter sold in Ireland to date has a Rsce of 33, so it may not be a problem for them to run with the standard.

There was some mention in the installers letter which seemed to indicate that they felt that a lower Rsce would allow a higher MEC – the Rsce relates to the maximum size of generator which can be installed, not to what it can export. The only relationship with size of MEC is that if you are limited in what you can install then this obviously limits what you can export.

In the attachment SE-Emissions they list compliance with EN 61000-3-11 and EN 61000 -3-12 for a number of Three Phase models,  which is fine, but there are other tests in EN 50549 which is why a Test Cert for EN50549 is required. Also this attachment did not reference single phase models.

As EN 50549 is a European standard I would expect that if Solar Edge are selling anywhere in the EU they should already have an EN50549 Test Cert.

In relation to the documentation submitted, they have provided a Test Cert for the UK G99, but this is Ireland so our requirements are different. Essentially conformance to EN 50549 means that most of the tests required in UK G99 were already done when the unit was tested to EN 50549. Similarly EREC G/5 is a UK standard and not relevant to Ireland.

A point for them to note is that the Protection Settings for Ireland are different for the UK so that the protection values shown on the UK G99 cert are unsuitable for use on ESB system.

The Test Cert supplied from Israel showing conformance to EMC requirements under EN 61000 – 6 is not of relevance to ESB – any standards to which the unit must conform are in EN 50549 and in the ESB Distribution Code.

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