Hoymiles problem, or grid voltage too high?

[sharpener]

What counts as high voltage? Normal seems to be more like 240-245, with the 255 peaks with full battery & sun shining.
I thought they were trying to gradually bring it down to nearer 200 in the long run, and 220-230 at the moment

Mine is quite high, and incandescent lamps did not last long. We are in a village 200m from the substation. It hovers between 244 and 248V most of the time, as measured by my inverter. In the last two days the recorded extremes are 242 and 249, doesn't seem to correlate with my generation at all. Noticeable dips at teatime, midnight and breakfast time.



I have a high voltage level warning set to 250V for 60 secs as I was concerned that with the voltage drop in the 20m cable run the PV inverter will trip out on over voltage, but it has never happened. Having just looked it up I see that it would actually require +15% for 1.5 secs i.e. 364.5V so there is a big margin.

I thought they were trying to gradually bring it down to nearer 200 in the long run, and 220-230 at the moment

I thought the reverse, that they were trying to tease it up so as to deliver more power with fewer losses. More PV coming onto the network would help with that. Spec is 230V + 10% but in practice they never really changed if from the old 240V + 6% standard, so it was a Euro-fudge, either way the max was 254.4, now 253. If you see 255 you are entitled to complain!

[nowty]

What counts as high voltage? Normal seems to be more like 240-245, with the 255 peaks with full battery & sun shining.
I thought they were trying to gradually bring it down to nearer 200 in the long run, and 220-230 at the moment

Legal voltage from DNO is 216.2V to 253V
https://www.spenergynetworks.co.uk/page ... anges.aspx

"In the UK, the declared voltage and tolerance for an electricity supply is 230 volts -6%, +10%. This gives an allowed voltage range of 216.2 volts to 253.0 volts."

So, for example, if your voltage is at the max end of 253V without your solar running, your solar export will add to it as the current flows out through your incoming grid cable. That depends on your SAG rate, typically drops by around 1V per 1kW imported or increases by 1V per 1kW exported, so with the standard 3.68kW of export allowance thats almost 4V extra.

Anecdotally I've heard that the DNO typically is not bothered if your voltage at your grid point is around 253V + 4V = 257V at your full export rate. By the time you measure it at your neighbour's house or the transformer its likely to be back to below 253V because of the voltage drop downstream between you and the next measuring point.

The voltage climbs even further upstream through your own internal wiring to your inverter(s). The G98 or G99 inverter standard says your inverter should cut out through overvoltage at 262.2V (for 1 second) or 273.7V (for 0.5 seconds). You can help prevent inverter trip outs a little by using a larger sized connection cable between your grid point and your inverter. That reduces the voltage drop between your inverter and your grid point, thus reducing the upstream increase at your inverter.

[Tinbum]

When I first moved to this house, about 20 years ago, I had a 1 year old welder that wouldn't work. I took it back and they tested it and said their was nothing wrong with it. I brought it home, wouldn't work but didn't have time to see why not.

A few weeks later I happened to measure our voltage, it was about 260v. Rang the DNO, they were down within the hour, tested it, said they had to cut the supply as it was dangerous but I persuaded them not to. A couple of hours later they had a crew down changing our pole transformer. It turns out it was only 5Kva and showed signs of lightning damage.

After that the welder was fine!! Turns out it won't start up if the voltage isn't within spec.

[Joeboy]

I went over to No1's place and switched off the AC. Sure enough red light flashing away. Took a good few minutes for it to self test and start outputting again. Would it be a simple process to run an extension reel to the Hoymiles and try again on a known AC line?

Just trying to prove if its on the property or outwith.

That's good that yours does the same - but yes, it seems to take a few minutes to reset itself & start working.
I think I should try it with the sunsynk turned off on a sunny day & see what it does.
It's mostly nice here today and it has dropped out a couple of times - I thought it might be ok as there have been multiple washing loads, dishwasher, soup cooking etc after our return from Norway.
If I look at the sunsynk voltage output it does seem to reach 254 or above when the hoymiles drops out.

I'd be contacting the dno at that overage.

[Stig]

Another anecdote about high voltage -no help to richbee (sorry) but maybe informative to others:
A work colleague has had trouble with his car charger due to high mains voltage (he measured it at 252V), the charger just displayed an error without any further information and the manufacturer suggested it might be an over-voltage protection. He then managed to charge the car off a 13A socket so the car didn't care. He doesn't have PV and this was after dark anyway.

I wonder if UK mains voltage has often been over 253V but we're only now seeing issues due to modern devices incorporating such safety cut-outs. I wonder what the spec. was before we harmonized with Europe: 240 +/-x%. Were teams dispatched nation-wide to adjust transformer tappings when the spec. was changed? Unlikely methinks...

[Countrypaul]

Nowty,

You may want to revise your last post, no way will the DNO be happy with 523V

[nowty]

Nowty,

You may want to revise your last post, no way will the DNO be happy with 523V

It took me about 5 mins reading my message over and over to find where I wrote that.

Now corrected.

[sharpener]

I wonder what the spec. was before we harmonized with Europe: 240 +/-x%. Were teams dispatched nation-wide to adjust transformer tappings when the spec. was changed? Unlikely methinks...

I think it was 240V +/- 6%. I am confident the upper limit was +6%, I think the lower limit used to be -6% also but got widened to -10% so it would include the then nominal 220V European supply voltage, the Euro-bodge referred to upthread. So nothing physically needed to be changed. (Ditto in Europe, their spec was 220 +10 -6.

Now we have a nominal 230V +10-6%, they have 230 '-10 +6.

Nothing has changed. Equipment has to tolerate 230 +/-10% which is 207 to 253. Everyone is happy.

40 years ago I served on the local IEE committee, the secretary was a senior distribution engineer. I remember someone complaining about his supply voltage and this guy saying he had the keys in his car and would change the transformer tap on his way home.

[Andy]

I am lucky to have a 13kW export limit, in practice I don't get to use it. On a blowy late spring sunny day exporting 13kW will take me well over 260V. I have had a few things suspiciously die around the time I did the tests and I didn't let the voltage climb much above 256V. So I limit my voltage to 250V whilst exporting though might sneak it up a bit this year. The lure of more export money is a strong motivator.

It's not worth tapping us down much more as we have the opposite problem when I am drawing a lot of current in the winter (80A) the voltage drops quite a bit reaching around 220V at the Quattro and then 217-218 at the CU.

[ecogeorge]

Last 7 day voltage max here 254.4v measured 400mm from CU. Varies between 240 and 250 normally.
Guess it's historical area for economy 7 and storage heater demand ............
Not hugely concerned as higher volts = less amps and less amps = less losses.
Inverters seem ok ,not noticed any tripping issues.
George.