AC V outrange error

Sito85

Hi all,

I have been getting the above message whenever the grid voltage goes above 253 V (now 257 V)

A bit of context:

Inverter is a Growatt MIN 3600TL-XE (no battery)
4kW/h worth of solar panels.

Our home load is usually pretty low and most of the energy is exported to the grid.

Whenever the solar generation reaches around 2.7kW/h or above, the grid voltage tends to go above 250V, which makes the inverter shut down for 180 seconds before starting back up.

I have increased the over voltage limit on the ShinePhone app up to 257 V but it keeps shutting down. I started with 1 V increments starting from the default 253 V limit.

Attached is a graph of an average day, where generation goes up until the system shuts down. I have read the inverter manual and it states that the inverter can work at up to 276 V, however I am unsure if it is safe to keep increasing the over voltage limit.

WindyMiller

Sito85 In your original picture you showed that the first outage happened at around 2KW at around 10.30am? If you had a battery that was timed to take the excess charge between say 10.30am and 3.30pm and could absorb the extra 1KW you might be able to keep the voltage down during the peaks of the day. In the summer time this might be between 8am and 6pm so you might need a battery with a spare capacity of around 5KWh (to absorb the excess over that 10 hours) to keep the voltage down. This energy would then be available to power the house or to export during the evenings. You might be able to get one for around the £2-3000 mark although it may take as much as 10 years to recover that cost. OK if you expect to live at that property for the duration and that you have the money to spare.

johalareewi

This could be a fault with the grid supply to your premises.
You should report it to your DNO via their fault line.

I had the same where my EV charger kept going offline due to over voltage errors.
Ohme said report to DNO which I did.
They came and checked the line and said yes, the grid was over voltage and they would need to fix it.

Sito85

johalareewi thanks for your quick reply. I have made a report and they have acknowledged it. They will send a technician to check and get back to me within 21 days.

KristianS

Yes, overvoltage is bad and if the DNO are not aware then things can get worse as you try and export more to the grid. Not good for unprotected electronics in the local area at all.

WindyMiller

There is a possibility that it is your house cabling that causes this - the cable from the street to your house I mean. When they do the test they ask you to turn off your solar inverter so that you are not pushing any power back to them. They measure the grid voltage and if it is below 253v (230v +10%) they will say it isn't their grid that's at fault.

Trouble with this is that the grid voltage naturally goes up and down during the day and they may not be testing it when the voltage is high. Also, due to the resistance of the cable, the voltage you see depends on the current flow and if you and any of your neighbours are pushing power back to the grid the voltage will naturally increase above what they measure.

In my case I was unable to persuade the DNO to reduce the voltage as they measured between 249 and 252v but I was seeing 257v during peak export of 6kW and my inverter was backing off for 5 minutes and even sometimes needed to be restarted as it had locked out. What made the difference for me was that the inverter manufacturer updated the firmware giving a bit more headroom before it backed off the grid.

The regulations give an absolute limit of what the voltage can go up to (and you don't want it too high as other things in your house could fail) but a limit of 257v is just too low to be useful in these scenarios. I think it's now set to 260v (Givenergy inverter so different to yours).

Sito85

WindyMiller That’s probably the issue, whenever I test the votage at any power point, the reading is ´normal´ (240-250 V), it is only when the solar panels are producing a good amount (2.5-2.8 kW) when the reading on the power point and on the inverter LCD goes above 253 V.

Hopefully that is something I can discuss with the DNO technician and come up with some solution.

My concern is, as you pointed out, that if I increase the over voltage limit and let the inverter work on 260 V, it also means that my appliances will also be on 260 V.

johalareewi

WindyMiller
When I reported my over voltage, the DNO took readings at the sub station and they were consistent with the readings they got at my meter. They put a monitor at my meter but I could keep my inverter running. A week later they did some tweaking overnight somewhere (main transformer?) and that sorted it out. YMMV.

WindyMiller

Sito85 I haven't had anything go pop and I'm pretty sure that in the height of summer we get voltages approaching 260v in the house during the afternoon when the sun is at peak zenith and the grid load is low. If you are concerned you can ask your installer to fit a voltage optimiser. Effectively this is a step down transformer that makes your house run at a lower voltage. They are a few hundred pounds. But it does mean that when you are generating power at the lower voltage it is stepped up to send it to the grid so actually makes the problem worse on the grid (all your neighbours see the higher voltage whilst you are below the 253v). If they measure again and believe you are causing the high voltage that might be a problem although it might make them reduce the voltage at the sub-station which is really what you want them to do.

WindyMiller

johalareewi They did that for me too but got the same readings at the sub-station i.e. below 253v so declined to fix anything unfortunately.

But yes try to get them to monitor it over a few days so that the real peak value is recorded. You can then keep your inverter on too.

WindyMiller

I just checked and my last Grid Voltage Fault was 8/4/24 at 257.7v just before my Inverter Firmware was updated so that was the fix in my case (well the problem became a hidden one).

PANface

Hi
As i understand it is, you are pushing electric into the grid that your "local neighbours" are not using so you have to push it further down the line.
If there is more solar than users the grid voltage will rise.

You should not exceed 253v pushing out.
Personally you don't want this as your washer/fridge/tv etc. are under pressure from high voltage as they will probably be rated 250v max.

Your inverter shuts down at 253v to protect against this for you and your neighbours.
Problem is if Mr Jones 3 doors down on the same phase as you has solar and has set his to push out upto 257v yours will shut down first at 253v.
DNO take a grim view of anyone pushing more than 253v out and could/should refuse to accept any of your generation.
With more and more people getting solar this is getting more and more common and are now refusing 3.68kw solar in some areas in the UK now.

Pushing 257v and buying a new washer/fridge every 2 years as you/your neighbour have frazzled them to gain export of an extra £100 per year could be a false economy.

Just saying
as I have same issue

WindyMiller

PANface I do agree with this but my experience was with a DNO that knew the limit was 253v and stated that measurements of 252v were therefore fine giving no headroom for generation. This means that virtually no solar can be exported as that extra volt would be consumed by just a few hundred watts of export.

The real issue is with a grid that wasn't set up for generation. 20 years ago setting the voltage to around 250v was fine as the grid voltage would only ever go down from this point and it meant electric fires/kettles/cookers were quicker to heat up. 20 years down the line and we want to export large amounts of energy (and quite frankly the country needs us to) but the DNO's do not want to go and reset their grids to a nominal 230v. They have chosen a piecemeal approach based on reporting and resist those that they can. If your own DNO does agree to dropping the voltage it means briefly interrupting the supply to your neighbours too whilst they move the taps on the transformers (well mostly, some can be done without interruption and even some can be done remotely). I think this means they have to inform them in advance that it is a planned interruption.

johalareewi

WindyMiller some can be done without interruption

My DNO didn't need any downtime but they did say there was only one person in the region who could do the work so they had to schedule it in. YMMV.

My over voltage reports were at night when I was not exporting so the DNO were happy to investigate. Ohme provided a spreadsheet of over voltage data (from the EV charger) for the DNO plus I had my inverter logs. DNO were confident the problem was their side but had to wait a while to fix it.

PANface

Interesting, i have overvoltage during export and at night i have undervoltage below 212v, dno have been out many times to me and iam tinkering on the edge.

i have limited my charger (zappi) and try not to draw more than 65amps at night.

seems okay at the moment

WindyMiller

PANface That does feel like a high impedance cable or connection somewhere. Are you fed from overhead wires that run a long distance? Generally distribution is done at much higher voltages than 230v eg 11Kv where a few volts lost are neither here-nor-there (and the current is proportionally less). But after the last step-down transformer that few volts becomes very significant.

The DNO can use motorised controllers which self adjust the voltage (effectively move the tappings) but I bet they're expensive to install so unlikely they would do that for 1 or 2 properties. But a whole area with the problem could be fixed this way.

You could probably get something yourself that's a bit like an adjustable voltage optimiser but these are lossy so you might lose a few % of power which could be expensive over time (at your expense to fix their problem).

PANface

WindyMiller

Not overhead but the very last house on the line, dno say if i wanted it sorting it would be at my cost of £22k to my drive only........
id have to generate alot to get that back!
I think if or more when any of neighbours get an EV we/I will be screwed, although maybe at that point they might upgrade the cable, who knows????

WindyMiller

PANface I fully understand the high costs they would charge. At my local Church we were blowing our 60A fuse (heat pumps, fan heaters etc.). When I asked for an upgrade I had a similar quote to replace the cable. Fortunately we had 2 feeds into the building at opposite ends of the premises. The other was a 3 phase 100A so we ran our own 100A 3-phase cable inside our property and re-wired the heavy loads onto this. Total cost £5000 with much more headroom for expansions.

KevinD

WindyMiller
Your mention of wiring up 3 phase always brings to mind a colleague who had the job of wiring up the pump house at brand new " Waste Water treatment facility " ( AKA " the sh*t works " ). He was an immaculate worker, the cable runs were impeccable which was why he was given that particular job. For some reason he had a major brain fart, as come switch on nothing worked. Turned out he'd run an individual phase to each pump. He was known as " Three Phase Tony " thereafter.

WindyMiller

KevinD Superb story.

After we had done the 3 phase cable upgrade we had a problem with the Organ blower pump. The changes meant it had been moved from one distribution board to another. It was also a 3-phase motor and was running backwards! We had to swap 2 of the phases over but I'm glad it wasn't pumping anything more than air! I guess someone in the past wasn't careful enough with identifying the phases properly.

Sito85

Would the issue (inverter shutting down due to grid voltage being too high) be resolved with a battery? Instead of pushing your excess production back to the grid, you’d store it at home, hence no increase on grid voltage nor competition with your neighbours to push your excess onto the grid.

WindyMiller

Sito85 Yes it would. Your battery would have to have enough spare room with an adequate charge current capacity to absorb all that the panels were producing which would then keep the voltage down.

My problem happened when the batteries reached full charge and the sun was still shining. There was nowhere else for the energy to go so it was sent to the grid.

If the grid power limit within the inverter is reduced then it won't raise the voltage by so much but then you won't receive all that you can for exporting the excess energy (the panels would be throttled back).

When the systems are approved for connection to the grid the authority permission is called a G98 or G99 document. The difference is that G98 can be connected without prior approval from the DNO (electricity board) but must be limited to 3.68KW. If you get a G99 before your installation the limit is specified and this can be above 3.68KW (mine is 6KW for example). When producing the G99 the DNO are supposed to work out how much energy they can accept and part of this should include how much the voltage might increase by when you are exporting your excess energy. The limit is programmed into your inverter which should then ensure it is not exceeded. However I cannot see how the DNO can predict what will happen with the votage when you do this and it seems many systems end up trying to put out the power limit by exceeding the voltage limit.