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Solar Voltage Rise, a spanner in the FIT works?

  • 23-03-2021 6:11pm
    #1
    Registered Users, Registered Users 2 Posts: 3,971 ✭✭✭


    I've hit a really unusual problem that is apparently quite common in countries where domestic solar is more widespread (Australia), Solar Voltage Rise

    My house is really really close to the transformer. I'm literally the only property on the transformer and there's probably only 50m of cable from it to my meter. So my voltage is typically around 243V at idle. Problem occurs when I feed in (not even a huge amount, 2kW sometimes), I end up popping the 253V limit and my inverter has to put on the handbrakes!

    This has little to do with the size of my setup, but more to do with my local grid supply. As the article above alludes, this will become more and more of a problem as more people get solar. It's not excess power that's the problem, it's excess voltage.

    I'm currently looking at solutions to fix this on my inverters themselves, but this could throw off people whose plans involve feeding in a lot of electricity in the Summer.


«1

Comments

  • Moderators, Home & Garden Moderators Posts: 6,280 Mod ✭✭✭✭graememk


    Yep bumped into that today too,

    Although, more voltage is more power to push more electricity out onto the grid, the inverter has to raise its voltage.

    Hits voltage limit and stop, then it slowly ramps the power back up again.


  • Registered Users, Registered Users 2 Posts: 3,971 ✭✭✭mp3guy


    graememk wrote: »
    Yep bumped into that today too,

    Although, more voltage is more power to push more electricity out onto the grid, the inverter has to raise its voltage.

    Hits voltage limit and stop, then it slowly ramps the power back up again.

    What inverter do you have? Curious to know your setup, distance from transformer, number of other properties on the transformer etc.. What your voltage is when the inverter is off / not supplying any power (from PV or battery).

    Fronius have a great video explaining the problem here (video linked at starting time) https://youtu.be/X8tsQhp7hM0?t=1137


  • Moderators, Home & Garden Moderators Posts: 6,280 Mod ✭✭✭✭graememk


    mp3guy wrote: »
    What inverter do you have? Curious to know your setup, distance from transformer, number of other properties on the transformer etc.. What your voltage is when the inverter is off / not supplying any power (from PV or battery).

    Fronius have a great video explaining the problem here (video linked at starting time) https://youtu.be/X8tsQhp7hM0?t=1137

    at least 5 properties, transformer is about 200 m away, about 5 properties, (2 with solar. although my parents wasn't exporting much)

    Currently at 237 on both mine and my parents house,
    Peaked at 251.1, Happened not long after battery finished charging.

    Solis inverters, a 6kw on mine, 5kw on parents, was generating 5.6kwish when it cut off, and most of it was being exported.

    No CT's on the inverters as they are within the limit.


  • Registered Users, Registered Users 2 Posts: 3,971 ✭✭✭mp3guy


    I took a peak at the Solis docs and it doesn't look like they have any voltage-based limiting functionality.

    Fronius and SolarEdge apparently do and as far as I can tell SolaX also does, but it's not very clear how to configure it properly from any manuals.

    Given the prevalence of Solis inverters in Ireland I reckon this is a ticking time bomb.


  • Moderators, Home & Garden Moderators Posts: 6,280 Mod ✭✭✭✭graememk


    mp3guy wrote: »
    I took a peak at the Solis docs and it doesn't look like they have any voltage-based limiting functionality.

    Fronius and SolarEdge apparently do and as far as I can tell SolaX also does, but it's not very clear how to configure it properly from any manuals.

    Given the prevalence of Solis inverters in Ireland I reckon this is a ticking time bomb.

    Does yours just currently cut out when it hits the limit?


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  • Registered Users, Registered Users 2 Posts: 3,971 ✭✭✭mp3guy


    graememk wrote: »
    Does yours just currently cut out when it hits the limit?

    Yeah, once the voltage hits the programmed limit (253V) it just dies. See output power:

    yokJ3f2.jpg

    And voltage:

    Ea5WOW8.jpg

    There are references to reactive power control modes and volt-watt response modes in the manual so I'm working with my installer and SolaX to figure out what's the right setting. This is only really a problem for export, won't affect self consumption.


  • Registered Users, Registered Users 2 Posts: 1,627 ✭✭✭quentingargan


    mp3guy wrote: »
    I took a peak at the Solis docs and it doesn't look like they have any voltage-based limiting functionality.

    Fronius and SolarEdge apparently do and as far as I can tell SolaX also does, but it's not very clear how to configure it properly from any manuals.

    Given the prevalence of Solis inverters in Ireland I reckon this is a ticking time bomb.

    [edit] Sorry - after posting I realised by voltage limiting functionality, you meant power limiting. That is not present on many brands, but you still lose production with it. It is better to see if you caan get permission to adjust the 253v limit up to 255 or 260. In UK, the limit is 264 because their nominal is 240. Ours is meant to be 230]

    You can adjust the voltage range on most inverters, including Solis, but you are then in breach of EN5048 (soon to be EN51545). ESB sometimes gives permission to do this but I have never seen them do so in writing.

    Your grid connection to the inverter should be on a cable heavy enough to ensure voltage drop <= 1%. I would try reading grid voltage at the consumer unit with a multimeter to check this isn't exacerbating the problem.

    This is often a problem on sites close to wind farms. When they roll out solar parks, it will get worse because their output will peak at the same times.


  • Registered Users, Registered Users 2 Posts: 3,971 ✭✭✭mp3guy


    [edit] Sorry - after posting I realised by voltage limiting functionality, you meant power limiting. That is not present on many brands, but you still lose production with it. It is better to see if you caan get permission to adjust the 253v limit up to 255 or 260. In UK, the limit is 264 because their nominal is 240. Ours is meant to be 230]

    You can adjust the voltage range on most inverters, including Solis, but you are then in breach of EN5048 (soon to be EN51545). ESB sometimes gives permission to do this but I have never seen them do so in writing.

    Your grid connection to the inverter should be on a cable heavy enough to ensure voltage drop <= 1%. I would try reading grid voltage at the consumer unit with a multimeter to check this isn't exacerbating the problem.

    This is often a problem on sites close to wind farms. When they roll out solar parks, it will get worse because their output will peak at the same times.

    Well there are two methods for limiting voltage as outlined by the Aus/NZ standard in the Fronius video, one is based on limiting exported power back to the grid when approaching the voltage limit. The other is about manipulating the power factor to leverage reactive power to control the voltage (not sure how much this affects the resultant exported power). Again, all this only impacts the power you feed back in, so only a problem if FIT is a big part of your plan. Otherwise, your inverter will keep cycling and you will lose self consumption power as well as exported.

    That's interesting to hear anecdotally the ESB might permit a higher voltage limit, I might see what I can do there. I'm not near any other (micro) generators, in a typical rural environment, just single phase.

    We've got 16mm2 through and through with the inverters so I think I'm alright cable size wise. I do have a voltage measurement at the consumer unit and down at the inverters and they concur.


  • Registered Users, Registered Users 2 Posts: 6,256 ✭✭✭Ubbquittious


    I must really install more solar panels. Rare enough to see over 230 these parts and below 220 is common. Some days my compressor wont even start the voltage is too low. Only 3 houses on the transformer I think


  • Registered Users, Registered Users 2 Posts: 3,971 ✭✭✭mp3guy


    ESB are coming out to install a voltage monitor for 10 days and then see what can be done / they're willing to do. Hoping they're flexible given there are no other houses on my transformer and likely never will be.


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  • Registered Users, Registered Users 2 Posts: 1,627 ✭✭✭quentingargan


    If someone has this issue happening on a Solis inverter, PM me. I may have a setting that can remedy it, but I would need someone on a site with this issue to test it.


  • Registered Users, Registered Users 2 Posts: 3,971 ✭✭✭mp3guy


    If someone has this issue happening on a Solis inverter, PM me. I may have a setting that can remedy it, but I would need someone on a site with this issue to test it.

    What's the setting, out of curiosity?


  • Registered Users, Registered Users 2 Posts: 12,136 ✭✭✭✭KCross


    mp3guy wrote: »
    ESB are coming out to install a voltage monitor for 10 days and then see what can be done / they're willing to do. Hoping they're flexible given there are no other houses on my transformer and likely never will be.

    They can, i think, change the windings in the transformer to lower your voltage which would be the opposite of the usual complaint!

    Or they might just swap out your transformer.

    Another likely prospect is that they say the voltage is within the spec of the regulator and hence do nothing.... thats what the voltage monitor will tell them. I've had that done on my house for low voltage. They have to do that to gather the stats in case you create an issue with the regulator. There are specific guidelines around what the voltage can/cannot be over a preiod of time.


  • Registered Users, Registered Users 2 Posts: 3,971 ✭✭✭mp3guy


    KCross wrote: »
    They can, i think, change the windings in the transformer to lower your voltage which would be the opposite of the usual complaint!

    Or they might just swap out your transformer.

    Another likely prospect is that they say the voltage is within the spec of the regulator and hence do nothing.... thats what the voltage monitor will tell them. I've had that done on my house for low voltage. They have to do that to gather the stats in case you create an issue with the regulator. There are specific guidelines around what the voltage can/cannot be over a preiod of time.

    I wonder if they'll ask me to turn off my solar inverters for the 10 days. I'm inclined not to (which means they'll record the voltage breaching 253V).

    It'd be the same if say I had low voltage around 210V and turned on our electric shower (which drops the grid reading by 9-10V last time I checked). They'd record < 207V, and would have to fix it.


  • Registered Users, Registered Users 2 Posts: 12,136 ✭✭✭✭KCross


    mp3guy wrote: »
    I wonder if they'll ask me to turn off my solar inverters for the 10 days. I'm inclined not to (which means they'll record the voltage breaching 253V).

    It'd be the same if say I had low voltage around 210V and turned on our electric shower (which drops the grid reading by 9-10V last time I checked). They'd record < 207V, and would have to fix it.

    Thats the kicker, they dont have to just because you get a few high or low readings.

    They are allowed some leeway over a period of time. Its all clearly laid out as to what the criteria for a pass or fail is. If it fails they have to fix it but a few high or low readings over those 10 days wont be enough for a fail.


  • Registered Users, Registered Users 2 Posts: 3,971 ✭✭✭mp3guy


    KCross wrote: »
    Thats the kicker, they dont have to just because you get a few high or low readings.

    They are allowed some leeway over a period of time. Its all clearly laid out as to what the criteria for a pass or fail is. If it fails they have to fix it but a few high or low readings over those 10 days wont be enough for a fail.

    Yeah that's what I'm worried about. Just gotta wait and see.


  • Registered Users, Registered Users 2 Posts: 12,136 ✭✭✭✭KCross


    mp3guy wrote: »
    Yeah that's what I'm worried about. Just gotta wait and see.

    Here's the result I got and the regulations, so you have an idea of what they are allowed "get away with"!

    https://www.boards.ie/vbulletin/showpost.php?p=106706752&postcount=57


  • Registered Users, Registered Users 2 Posts: 3,971 ✭✭✭mp3guy


    KCross wrote: »
    Here's the result I got and the regulations, so you have an idea of what they are allowed "get away with"!

    https://www.boards.ie/vbulletin/showpost.php?p=106706752&postcount=57

    Oh nice, thanks for linking that. How did you resolve things in the end?


  • Registered Users, Registered Users 2 Posts: 12,136 ✭✭✭✭KCross


    mp3guy wrote: »
    Oh nice, thanks for linking that. How did you resolve things in the end?

    The original problem with the HP tripping was resolved by increasing its trip limit!

    The HP manufacturer guided me on how to do that.

    I havent had any issues since and ESB didnt do anything eventhough my voltage went down to the low 200s during their test.


  • Registered Users, Registered Users 2 Posts: 2,830 ✭✭✭air


    ESB Networks are proposing to introduce on load tap changing transformers to mitigate the likes of this issue.
    I heard it said with regard to increasing the capacity of the local distribution network to facilitate heat pumps and EVs but of course they would also work in reverse for PV.

    In the OPs case with a dedicated transformer a manual tap change would seem sensible if the transformer in question allows for it, I'm not sure the smaller ones are adjustable though.

    They could pick a set point at the ideal point in the allowed range to balance your MIC and allowed export capacity.


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  • Registered Users, Registered Users 2 Posts: 6,256 ✭✭✭Ubbquittious


    air wrote: »
    ESB Networks are proposing to introduce on load tap changing transformers to mitigate the likes of this issue.
    I heard it said with regard to increasing the capacity of the local distribution network to facilitate heat pumps and EVs but of course they would also work in reverse for PV.

    In the OPs case with a dedicated transformer a manual tap change would seem sensible if the transformer in question allows for it, I'm not sure the smaller ones are adjustable though.

    They could pick a set point at the ideal point in the allowed range to balance your MIC and allowed export capacity.


    Interesting. I'd say you could be waiting a long time for one of those transformers if you're in the shticks


  • Registered Users, Registered Users 2 Posts: 6,256 ✭✭✭Ubbquittious




  • Registered Users, Registered Users 2 Posts: 1,627 ✭✭✭quentingargan


    mp3guy wrote: »
    What's the setting, out of curiosity?
    I tried this setting since on an inverter here and the option isn't available for the Irish grid standard. Solis says they may correct this on future versions of the firmware.


  • Registered Users, Registered Users 2 Posts: 3,971 ✭✭✭mp3guy


    Just found out about voltage optimisers: https://energyace.co.uk/voltage-optimisation-residential/

    Anyone heard about these before?


  • Registered Users, Registered Users 2 Posts: 2,830 ✭✭✭air


    Yes, run, a mile!


  • Registered Users, Registered Users 2 Posts: 3,971 ✭✭✭mp3guy


    air wrote: »
    Yes, run, a mile!

    Would be great if you could expand on this. Used one before?


  • Registered Users, Registered Users 2 Posts: 3,971 ✭✭✭mp3guy


    Looks like another brand is available: https://www.nuvisionenergy.co.uk/opti-volt-100

    Not really paying any attention to the "SAVES YOU MONEY" aspect, more the fact it allows tapping down of the grid voltage entering the property and works with PV.


  • Registered Users, Registered Users 2 Posts: 2,830 ✭✭✭air


    They're a scam basically, different outfits have been pushing them for years.
    The whole premise they're based on is false and there is next to nothing in the magic boxes generally.


  • Registered Users, Registered Users 2 Posts: 3,971 ✭✭✭mp3guy


    air wrote: »
    They're a scam basically, different outfits have been pushing them for years.
    The whole premise they're based on is false and there is next to nothing in the magic boxes generally.

    Sorry, are you saying they categorically do not decrease the voltage? So if I buy one and measure the voltage on the input and output, it will be the same?


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  • Registered Users, Registered Users 2 Posts: 2,830 ✭✭✭air


    For many of them that will be the case, but even if they do they're not going to save you money or solve your issues with voltage rise.

    For a given export power and grid voltage you're going to see a fixed rise in voltage at your metering point.

    Whatever you put between your metering point and your PV inverters and / or loads can't change this fact.

    You risk causing even more issues in fact if you got one that did reduce voltage as your inverter would be fooled into thinking the grid voltage at your metering point was lower than it thinks
    It could keep exporting to a level that causes the voltage at your metering point to exceed the maximum voltage limit set out by EN50438.

    So as I see it you risk violating the grid interface standards by installing one of these on a connection with micro generation.

    All told, they are a waste of time and money and are in general sold by unscrupulous operators in my experience.
    That's all I have to say on them.


  • Registered Users, Registered Users 2 Posts: 3,971 ✭✭✭mp3guy


    That was something I wondered. If the grid is providing 244V, and a "magic box" taps it down to 234V for me, my inverter sees that and exports all the up to 245V (on the house side of the magic box), does this rise in voltage then pass back through the box to mean I'm really feeding in at 255V?

    Sounds like you're heavily biased against the proprietors of these items :) I might ring them and run this by them to see what they say.

    Do you think I have options if my inverter supports reactive power control?


  • Registered Users, Registered Users 2 Posts: 2,830 ✭✭✭air


    I'm not biased against anyone that sells real products that serve a useful function in an honest and transparent manner.

    I've encountered honest reps working for companies selling them before that were genuinely naive and or just lacking the technical understanding required to realise that they're BS.

    At most they will have an autotransformer inside.
    Reactive power control won't help your situation.

    If you do a cursory internet search you'll find plenty of horror stories on the subject.
    You're obviously disregarding my advice if you're going to ring them so best of luck with it.


  • Registered Users, Registered Users 2 Posts: 3,971 ✭✭✭mp3guy


    air wrote: »
    I'm not biased against anyone that sells real products that serve a useful function in an honest and transparent manner.

    I've encountered honest reps working for companies selling them before that were genuinely naive and or just lacking the technical understanding required to realise that they're BS.

    At most they will have an autotransformer inside.
    Reactive power control won't help your situation.

    If you do a cursory internet search you'll find plenty of horror stories on the subject.
    You're obviously disregarding my advice if you're going to ring them so best of luck with it.

    I try to avoid believing what strangers post on the internet. In particular this sub forum has had a sizeable amount of misinformation on it before so I'm inclined to take everything with a pinch of salt.

    I would love concrete evidence from you (and conversely from companies selling these items). Haven't made any decisions yet, but don't get too uppity if I don't take air's unverifiable word as truth. Any links to those horror stories? Anyone I can contact with first hand experience? Datasheets? Did a quick search myself and couldn't find anything.


  • Registered Users, Registered Users 2 Posts: 2,830 ✭✭✭air


    mp3guy wrote: »
    does this rise in voltage then pass back through the box to mean I'm really feeding in at 255V?

    Yes, of course, this is exactly what I said in my previous post.
    If you put a transformer between your inverter and the grid, you stand to export to such an extent that you will cause the local grid voltage to exceed that which is allowed.
    You could find yourself liable for the consequences of this if it happens as a result of you installing uncertified equipment.


  • Registered Users, Registered Users 2 Posts: 2,830 ✭✭✭air


    mp3guy wrote: »
    I try to avoid believing what strangers post on the internet. In particular this sub forum has had a sizeable amount of misinformation on it before so I'm inclined to take everything with a pinch of salt.

    I would love concrete evidence from you (and conversely from companies selling these items). Haven't made any decisions yet, but don't get too uppity if I don't take air's unverifiable word as truth. Any links to those horror stories? Anyone I can contact with first hand experience? Datasheets? Did a quick search myself and couldn't find anything.

    Well why are you asking questions if you're not interested in taking anyone's word for it.
    You obviously know noting about the subject, I know plenty and have invested enough time to explain the issues around them to you.
    If you want to disregard my advice, that's well and good and your own prerogative, but you can do your own leg work.
    What possible motivation could I have for talking down a particular product?
    Good luck.


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  • Registered Users, Registered Users 2 Posts: 3,971 ✭✭✭mp3guy


    air wrote: »
    Yes, of course, this is exactly what I said in my previous post.
    If you put a transformer between your inverter and the grid, you stand to export to such an extent that you will cause the local grid voltage to exceed that which is allowed.
    You could find yourself liable for the consequences of this if it happens as a result of you installing uncertified equipment.

    Hence why I'll ask them if this happens. If they say yes, then it's obviously a non-starter. If they claim this doesn't happen, well then either they're lying, don't know or are doing something different to your assumption.
    air wrote: »
    Well why are you asking questions if you're not interested in taking anyone's word for it.
    You obviously know noting about the subject, I know plenty and have invested enough time to explain the issues around them to you.
    If you want to disregard my advice, that's well and good and your own prerogative, but you can do your own leg work.
    Good luck.

    You're right, I don't want people's word. I want concrete verifiable facts. Too much to ask for obviously. Anyone can say "I know plenty".


  • Registered Users, Registered Users 2 Posts: 2,830 ✭✭✭air


    What facts do you want?
    These boxes do nothing useful, it's hard to prove a negative.

    Generally if they have anything inside, it's a small autotransformer that reduced the grid voltage slightly as it enters the house.
    This will have the opposite effect on export obviously.

    What mechanism do you postulate they employ that will manage to limit your voltage to?
    How about you provide some facts yourself, post up a link or datasheet to a specific unit and I'll happily review it.


  • Registered Users, Registered Users 2 Posts: 2,830 ✭✭✭air


    mp3guy wrote: »
    Hence why I'll ask them if this happens. If they say yes, then it's obviously a non-starter. If they claim this doesn't happen, well then either they're lying, don't know or are doing something different to your assumption.

    Assuming this unspecified unit is the typical type with an autotransformer, the only way it won't create a (medium term) voltage rise issue is if it has on load tapping, which I doubt it will as they're generally made as simply and cheaply as possible.

    If it does have it, then it won't exacerbate the voltage rise issue but neither will it leave you any better off than where you started.

    Again, if you had even a vague idea of what it was you were hoping to achieve it would be helpful.
    There is no magic bullet that will allow you to push more energy onto a wire without raising it's voltage - physics 101.


  • Registered Users, Registered Users 2 Posts: 3,971 ✭✭✭mp3guy


    air wrote: »
    What facts do you want?
    These boxes do nothing useful, it's hard to prove a negative.

    First hand account/measurements would be ideal. e.g. "I bought one and here's a photo of the voltmeter proving it does X and doesn't do Y". Or, checkout this other forum where someone bought one and things went belly up.
    air wrote: »
    What mechanism do you postulate they employ that will manage to limit your voltage to?
    How about you provide some facts yourself, post up a link or datasheet to a specific unit and I'll happily review it.

    I postulate nothing, not my area of expertise, hence asking for information, not unverifiable opinions and assumptions.
    air wrote: »
    Again, if you had even a vague idea of what it was you were hoping to achieve it would be helpful.
    There is no magic bullet that will allow you to push more energy onto a wire without raising it's voltage - physics 101.

    I don't want to push more energy onto a wire? I want to prevent my inverter from shutting down. I don't care about pushing power out, just want to stop it cycling. Do you think Fronius's reactive power control solution is also bogus then? https://youtu.be/X8tsQhp7hM0?t=1592. It's based on reactive power control but you said that doesn't help, seems to be in contradiction.


  • Registered Users, Registered Users 2 Posts: 2,830 ✭✭✭air


    I haven't given you any opinions whatsoever, I've explained what i expect is inside and how it works and what the issues it cause are.

    I've only just clicked the link you provided and it all but confirms what I've been saying.
    It says (3 Tappings of 4%, 6%, 9%) which all but guarantees that it's an auto transformer and will behave exactly as I have described.

    How about you ask the supplier to confirm that it is in fact an auto transformer, then go an educate yourself on what an auto transformer is and how it operates and decide whether it will help you or not.

    I haven't looked into the Fronius solution you'll need to investigate the specifics of EN50438 for voltage lag and lead to see if it will help here, I'm fairly sure it won't but I don't have a copy of the full standard.
    That video is referencing a New Zealand grid standard by the looks of it.


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  • Registered Users, Registered Users 2 Posts: 2,830 ✭✭✭air


    mp3guy wrote: »

    I don't want to push more energy onto a wire? I want to prevent my inverter from shutting down. I don't care about pushing power out, just want to stop it cycling.

    The OP was interested in having his PV operate at full capacity.

    If you only want to limit export such that your inverter doesn't shut down due to over voltage then you could create a relatively simple voltage sensing circuit that would in turn modulate the DC input to the inverter proportionate to the grid voltage.
    I've seen this done before for different reasons and it would likely work on any inverter and not create any risks of non conformance on the AC side.


  • Registered Users, Registered Users 2 Posts: 3,971 ✭✭✭mp3guy


    air wrote: »
    I've only just clicked the link you provided and it all but confirms what I've been saying.
    It says (3 Tappings of 4%, 6%, 9%) which all but guarantees that it's an auto transformer and will behave exactly as I have described.

    That's just the Optivolt one, what about the Energyace one? That specifies "Choice of 4 voltage reduction settings (-10v, -15v, -20v, -25v)" which implies it works differently, i.e. it doesn't just tap down by a percentage, it's an absolute reduction. Same tech?
    air wrote: »
    How about you ask the supplier to confirm that it is in fact an auto transformer, then go an educate yourself on what an auto transformer is and how it operates and decide whether it will help you or not.

    That's the plan.
    air wrote: »
    I haven't looked into the Fronius solution you'll need to investigate the specifics of EN50438 for voltage lag and lead to see if it will help here, I'm fairly sure it won't but I don't have a copy of the full standard.
    That video is referencing a New Zealand grid standard by the looks of it.

    Yes I'm trying to find out if there's anything said about it in the standard.
    air wrote: »
    If you only want to limit export such that your inverter doesn't shut down due to over voltage then you could create a relatively simple voltage sensing circuit that would in turn modulate the DC input to the inverter proportionate to the grid voltage.
    I've seen this done before for different reasons and it would likely work on any inverter and not create any risks of non conformance on the AC side.

    Now this sounds pretty cool, who did it? How? Links?


  • Registered Users, Registered Users 2 Posts: 2,830 ✭✭✭air


    mp3guy wrote: »
    That's just the Optivolt one, what about the Energyace one? That specifies "Choice of 4 voltage reduction settings (-10v, -15v, -20v, -25v)" which implies it works differently, i.e. it doesn't just tap down by a percentage, it's an absolute reduction. Same tech?
    Sounds like just marketing spin to be honest, they've just converted the percentages to voltages I'd say.
    But the bigger point is that, either way, it's of zero use to you whatsoever - I'm not sure why you're still entertaining them at this point as you seem to understand the operation now.

    mp3guy wrote: »
    Now this sounds pretty cool, who did it? How? Links?
    It was some Australian guru with an off grid setup, there was no further details than what I described but it would be fairly simple to replicate with an arduino or similar. I haven't time to go searching for it.

    Read the AC voltage X times per second and modulate the gate of a high voltage MOSFET on the DC input to the inverter accordingly.

    If you have a look at OpenEnergyMonitor architecture and their PV diverters, a simpler version of the hardware used there could be modified to achieve it.

    If I recall correctly he hadn't even added a capacitor on the input, just chopped the PV input and that was it.


  • Registered Users, Registered Users 2 Posts: 3,971 ✭✭✭mp3guy


    air wrote: »
    It was some Australian guru with an off grid setup, there was no further details than what I described but it would be fairly simple to replicate with an arduino or similar. I haven't time to go searching for it.

    Read the AC voltage X times per second and modulate the gate of a high voltage MOSFET on the DC input to the inverter accordingly.

    If you have a look at OpenEnergyMonitor architecture and their PV diverters, a simpler version of the hardware used there could be modified to achieve it.

    If I recall correctly he hadn't even added a capacitor on the input, just chopped the PV input and that was it.

    Sounds pretty cool but a little out of my own comfort zone.

    I think I found at least a copy of EN 50438:2013 here https://shop.gwl.eu/docs/web/2018/EN_50438_2013-BS.pdf and it seems to state in section 4.5 that "In order to avoid disconnection due to the over-voltage protection the micro-generating plant is allowed to reduce active power output as a function of this rising voltage. If this function is activated, the micro-generating plant may reduce active power according to a logic chosen by the manufacturer. Nevertheless, this logic shall not result in steps of output power. " so it sounds like it's allowed.


  • Registered Users, Registered Users 2 Posts: 2,830 ✭✭✭air


    Sounds good and good work on finding a copy of the standard for free.

    It's a sensible solution for sure at a grid level but again not much use to the OP.

    Also I just watched a minute or two of that video but he mentions that the volt watt limiting is only active when the inverter is at full power, which likely means it will be of little or no benefit to you either.

    It wouldn't take much for Fronius to allow full output shaping in response to grid voltage and it would make their products a lot more useful for people off grid also.

    Given your automation experience etc I expect you could construct a DIY power limiter very easily, you'd just need to be mindful of the hazards of the DC voltages at play.


  • Registered Users, Registered Users 2 Posts: 3,971 ✭✭✭mp3guy


    I finally had the ESB out. They stuck a voltage monitor on at my meter for about 10 days. The engineer shared the data with me, it was well below 250V the entire time, usually around 244V.

    He did some live measurements at various sockets for me too (with two different meters) and was getting 244-246V while the two inverters/Zappi would read from 248V-250V. So it appears that they read high, quite high, 4V high! The engineer suggested maybe upping their internal limits to see if that stops them cycling, and maybe getting my own multimeter to read voltage at sockets in the house to be sure. But as far as they're concerned, it's not a problem.

    He did say the solution would be to move the transformer further away from me, which would involve doing work on my neighbour's land. So I've a few options.


  • Registered Users, Registered Users 2 Posts: 2,830 ✭✭✭air


    It's still on the high side for sure though.
    Are your inverters close to you main board? If they were a long way away, there might be scope to upgrade the supply cable perhaps although really clutching at straws.
    You don't have much leeway between your average grid voltage and the upper limits.


  • Registered Users, Registered Users 2 Posts: 12,136 ✭✭✭✭KCross


    mp3guy wrote: »
    I finally had the ESB out. They stuck a voltage monitor on at my meter for about 10 days. The engineer shared the data with me, it was well below 250V the entire time, usually around 244V.

    He did some live measurements at various sockets for me too (with two different meters) and was getting 244-246V while the two inverters/Zappi would read from 248V-250V. So it appears that they read high, quite high, 4V high! The engineer suggested maybe upping their internal limits to see if that stops them cycling, and maybe getting my own multimeter to read voltage at sockets in the house to be sure. But as far as they're concerned, it's not a problem.

    He did say the solution would be to move the transformer further away from me, which would involve doing work on my neighbour's land. So I've a few options.

    You'd need a friendly local ESB engineer to get that work sanctioned.

    As you said, technically there isnt a problem on their end.... they are within spec so are very unlikely to go moving transformers to satisfy your requirements, but you can but ask!

    What you really need are a few new neighbours drawing off the same transformer! ;)


  • Registered Users, Registered Users 2 Posts: 3,971 ✭✭✭mp3guy


    KCross wrote: »
    You'd need a friendly local ESB engineer to get that work sanctioned.

    As you said, technically there isnt a problem on their end.... they are within spec so are very unlikely to go moving transformers to satisfy your requirements, but you can but ask!

    What you really need are a few new neighbours drawing off the same transformer! ;)

    Actually he was very friendly, gave me his boss's office number and his own mobile number, said to let him know if I wanted to go any further with it.


  • Registered Users, Registered Users 2 Posts: 60 ✭✭Scoobydoobydoo101


    @mp3guy What was the end outcome here? Who did you contact to monitor the voltage?

    It sounds like I have a similar issue. On days where I am feeding into the grid the voltage is up around 252v and the inverter is faulting out.

    Can/will this do damage to the inverter long term?



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