Am I going daft, watched a video, using auto transformer, and it makes no sense to me?

[ericmark]

I know our power supply is 230 volts +10% -6%, so the supply is 216.2 to 253 volts. If the volts are higher or lower, then our solar panels, EV charging points, etc, should auto disconnect, this is for safety. I can't see how we are permitted to lift or drop the volts using an auto transformer to kid the solar, EV or battery charging that the supply has not gone out of spec.

This seems totally out of order to me. Other users on the supply will either be getting over or under voltage due to the auto transformer. Using the voltage optimiser to correct the voltage to current-using equipment I can understand, although I would not call what he fitted a voltage optimiser, it is a simple auto-transformer, the voltage optimiser would auto change tappings. The device did not auto change, but simply lifted the supply voltage to over the permitted 253 volts for all other users.

G99 approval I assume says we have looked at the system you're going to install, and are satisfied it will not cause the lines to be overloaded or the voltage to go out of specification. And since the solar without the auto transformer will not cause the voltage to go out of specification as it will auto close down, then OK go ahead. I am sure it does not say, we will import what ever you can produce? Or does it? As I try reading it says

Here are the main options you have if your G99 gets rejected:

1. Pay the DNO for grid upgrades
2. Limit your inverter at 3.68kW
3. Don’t connect to the grid
4. Apply for a G99 again at a later date

So one would assume the reverse is also true, if not rejected you can export over 3.68kW, and you don't need to pay for the upgrade to the system, I would assume the upgrade would be that transformer will include some auto tapping so it can adjust tapping for import and export situations.

But that does not mean the user can fit an auto adjusting transformer does it?

I have re-watched and it seems the solar panels were going over voltage

so there most have been a fault with the inverter. I wonder what he measured before he started, at 230 volts at the transformer to stay below 253 volts at the property, with 17 kW or 74 amps, the line - neutral loop impedance must be under 0.31Ω. If set to 240 volts, then 0.18Ω, so before installing such a massive solar array, one would look at the no load volts, and the loop impedance.

I would have thought if the loop impedance was above 0.20Ω then the job is a non starter. Even with the best auto stepping transformer more than 0.20Ω must be non starter.

Depending on cable runs, one must insure the solar auto disconnects before the PEN failure disconnects, and when producing so much power, one has to ask is a PME supply with overhead cables really the right option? Go to TT and no need for PEN failure device.

 

[blup]

Its entertainment as much as instruction.

 

[ericmark]

Its entertainment as much as instruction.

You're likely correct, he is on the maximum allowed with single phase, so he must have known it was on the edge. So 148 amps differential, and this needs to be within 36.8 volts, so line - neutral loop impedance needs to be better than 0.25Ω, and that's with the no load voltage mid-range, so 234.6 volts. With cable length to transformer, and other homes off the same supply, he must have known it was going to produce problems. Likely hoped the supplier would up-grade for free, but with that video, if the supplier sees it, more likely they will disconnect until solar panel inverters are set up correctly so can't cause over-voltage.

 

[flameport]

But that does not mean the user can fit an auto adjusting transformer does it?

They cannot.

Years ago there were various bandwagon companies installing such things and calling them 'solar optimisers' and other such nonsense. Mainly so they could sell £100s of additional equipment to the end user and crank up their profits.

Today the use of such things is specifically prohibited in both G98 and G99.

 

[ericmark]

I had a feeling it would not be permitted. I can understand why someone may break the rules, but to tell everyone on YouTube what you have done is unbelievable. I would not tell a soul if I did that, can't believe he has told everyone. I found another video

where he is staging off someone who has done something far less naughty things to what he did.

 

[ericmark]

There has been an update

he has agreed he did do things which were not really kosher, and the final outcome was a three-phase supply, it seems he should not have been allowed to export that amount on a single phase, he should have been limited to 5 kVA, but it was not his error.

Still, seems a likely 25 amp export per phase is rather high, I would need a second set of fuses, but seems sorted.

 

[SUNRAY]

Opinions please:
He states the house CU has to be changed to 3ph but the pool CU doesn't.
Am I the only one who see's no immediate requirement to change the house to 3ph?

In fact If my assumptions are correct and the predicted route for the new UG cable passes the garage, I'd suggest moving the incoming supply to the garage where the 3ph requirement is and run a 1ph submain from there to the house.

 

[ericmark]

As you say, the car charging and solar are the problem. Rest could stay at single phase. However, in my own 5 kW system, the idea is to not use the grid as a battery. I don't want to feed into grid at 2 pm, and then run the house off grid at 2 am. That will happen in the winter, but in summer I want the battery to bridge the gap when solar is not producing.

So I see the purple line dip at 9 am, and by 12:20 my battery is full, and I am exporting until 7:30 pm, hard enough to ensure the dishwasher, washing machine and tumble drier run when I have loads of solar with single phase, to ensure it runs for free with three-phase, would be even harder.

Why anyone would want 17 kW I don't know, but per phase it is only 5.6 kW only a little larger than my own, and using the shower I still import, so unless all shared between phases, it would still mean winter they would be importing.

I would assume the main point is to run the EV for free. But since, in the main, we use cars in the day, it would need something like the old Bedford CF system where the battery can be dropped and van rolled over the new charged battery, so the battery can be charged in the day.

When I was with British Gas, I was on an EV tariff, and that was midnight until 5 am, I really wanted power 10 pm to 3 am as charging until 5 am just resulted in exporting earlier in the morning, it takes around 1.5 hours to recharge a battery, assuming no limit to charge rate, other than the battery.

But any solar panels in one's area, means high voltage midday until sun set, and a lower voltage sunset until batteries run out, then even lower voltage until sun rise, as more and more homes fit solar the voltage is likely to rise, at the moment just past midnight at

what point will the DNO have to put up their hands and say sorry, no more. I have never seen 230 volts here.

 

[SUNRAY]

I thought it isn't a battery system

 

[ericmark]

I thought it isn't a battery system

No, he says there are three batteries, he did not say what size, just they are big, and he's problem was charging it at night he was going under voltage, and with solar in the day he was going over voltage, not sure how he went over voltage as my solar inverter will auto switch off with over voltage, and go to island mode with under voltage.

The set-up is large I had not considered the size compared with mine, but it is about three times the size in kW output, and he has it seems three inverters, each seems around double the size of my inverter. He says 62 panels, I have 14 that can produce 6 kW although limited to 5 kW as inverter only 5 kW.

Looking at what he shows, I would have thought that was more like 34 kW to 17 kW he claims. Although 100 amps is 23 kW so that would have been the limit.

But, as I found, as the battery size increases, the gains from off-peak diminish. And to get the super low tariffs, you need to give the control to the supplier.

Some of what he says does not seem to make sense. I don't have an EV, but my battery can charge at 60% of its kWh rating or the size of the inverter, so he has 17 + 7 = 24 kW he can charge at, the car EV charger will likely throttle that back to 23 kW, so we are looking at 174 amp difference within 36.8 volts difference, so loop impedance would need to be 0.21Ω or less, or an auto stepping transformer.

You note he does not say what reading he got. Personally, if I had made an error like that, I would be keeping quiet, not shouting about it from the roof tops. But it seems for him it worked, he got three phase for nothing.

 

[SUNRAY]

Apologies, I watched the original ages ago and only skimmed the second.

If the intention is to charge the batteries on cheap rate then I see no reason to put the house on 3ph and my original thought of installing the new 3ph supply to the garage wall still feels OK (assuming the garage is the building in front to the right.

 

[ericmark]

Although technically he asked permission and did as he was told, and the only thing he did wrong was use an auto transformer. The idea of not testing before such a large installation seems wrong.

The Summer and Winter use of solar and batteries is very different. At the moment, my battery dips to 19% and only grid use is the shower, I do not need an off-peak tariff, it would mean I pay more, as the charge for off-peak, is higher than what I get for export.

Winter very different, but even then, not that many days when state of charge does not hit 100% at some point of the day. September 11 days, October 4 days, November 11 days, December 10 days, January 15 days, February 15 days, March 2 days. I can't go back to see how bad those days were, just those days, no export.

There may be more of a problem when charging an EV, but as the battery size goes up, there is less and less benefit with off-peak tariffs.