Over voltage solar inverter shut down.

[John J]

This afternoon I noticed there was no generation from my solar panels despite the sun blazing down. A quick check showed the incoming mains voltage had risen to 258 volts, 5 volts above the 253 expected high limit. I called northern powergrid and a response van duly turned up but by then the sky had clouded over. The mains voltage had gone down by then and my panels kicked in again. The power grid guy mentioned my area has a lot of rooftop panels. Many seem to have higher over voltage tolerance before shutting down. I can see a developing problem if solar panels become more popular. I don't want to spend all summer watching my inverter output sitting at zero for hours.

[Theo]

At the end of the day the power has to go somewhere and, if not enough people in your neighbourhood are consuming, your mains voltage will rise. The grid isn't able to accept unlimited amounts of power (there will be some limit on your substation feeding back into the HV grid, although I'm not sure what the constraints are here).

So it seems you need to increase your local consumption. A solar diverter to heat your hot water tank is a quick fix, or look into a battery for timeshifting that power to when you do use it.

Theo

[N_Cook]

I keep asking PV tech people what the term is, but no joy so far. Nationwide in Germany, height of summer at midday, and low consumption of electricity , they have to dump electricity, which is not possible AFAIK. What they do is pay a fortune, whether required or not, to neighbouring countries to divert this surplus immediately to consume the excess. At least they do know the weather sufficiently in advance, to arrange this on the day, so no actual surprises

[Andrew]

It's mother natures way to cancel out some of those juicy RPI-linked increases payable on FITS's :-)

[Mark Carver]

A house in our village burst into flames on Saturday afternoon.

The fire service quickly (within a few hours) said the source of the blaze was the solar panels. Presumably  there are low voltage/high current connections that can become 'hot-spots' ?

[SH]

[Andrew]

Was the inverter up in the loft ?. They need a lot of ventilation.

[Andrew]

There is an article in todays DT from National Grid, suggesting that there should be regional electricity pricing so that they don't have to pay renewable companies to NOT produce so much windy power in the North when most of the demand is in London and the south.

Seems like they need to upgrade the transmission links connecting the North and the South.

[John J]

The system worked just fine for close on eight years. Then lots of rooftop arrays spread around the area served by the nearby substation. Two years ago following an unplanned power outage which ended following some switching round of the hv network a sunny day caused inverter shutdown. At that time the day voltage was 261 and night voltage 251. Following complaint at the time there was a brief outage and things went back to normal operation with night voltage 250. I figured the hv feed had been restored to normal routing. Co incidentally we had a village problem where some houses suffered extremely low voltage before the village was switched off then restored shortly after. This was said to be loss off one hv overhead line conductor and I guess the fault was switched out in favour of alternative source route. Today has been mixed weather with noticeable voltage variation from 251 under cloud and 255 when the sun came out sporadically.. Someone mentioned restriction of power transfer from the LV to HV at the substation. I really can't see how this would be achieved in a pretty unsophisticated village sub which contains a couple of oil circuit breakers and a transformer.. Perhaps someone can give some thoughts? Power flowing "up" to the grid would be matched by reduction of grid feed from one or more of the larger generators.

[John J]

I'm never convinced by fire service verdicts having followed them into the remains of a house fire they blamed on a storage heater. The heater exterior was blackened with bits of melted /burnt foam cushion stuck to it yet the inside was pristine. You might also find that available maximum DC short circuit current from a panel is pretty low, generally below 15A with connection cabling and joints rated well in excess of this to meet required standards.

[Andrew Gabriel]

DC at several hundred volts generates lovely arcs though.

Andrew

[Mark Carver]

10 days on, and the house is fenced off as if it's a crime scene. When I walked past a week ago, there was a bloke taking photographs with an SLR of the roof tile fragments on the driveway. What's all that about, I wish I'd asked him now ?

[harry]

The problem is probably cause by your local transformer being too small. i had exactly the same problem. This is especially true if you are in a rural area with a small pole type transformer. In my case the transformer was only 7KVa. It was old so they changed it for a 40KVa one. I have 8KW of solar panels, no problem now.

They might be able to change the tappings on the existing transformer, We're now supposed to be on 220V now, not 240V

[harry]

The problem is probably cause by your local transformer being too small. I had exactly the same problem. This is especially true if you are in a rural area with a small pole type transformer. In my case the transformer was only 7KVa. It was old so they changed it for a 40KVa one. I have 8KW of solar panels, no problem now.

They might be able to change the tappings on the existing transformer, We're now supposed to be on 220V now, not 240V

[Tim+]

No we’re not. “nominal supply voltage is 230 V +10%/−6% to accommodate the fact that most transformers are in fact still set to 240 V. “

Tim

[John J]

The particular substation serving me is inside a locked building about the size of a garage so I can't see the transformer. I do know it also serves a lot of houses now, having seen a number of new estates built over the last ten years. Currently Northern Powergrid have gone quiet although I'm still seeing out of tolerance voltages when I check the supply from time to time. Having woken up for a drink after midnight a few days ago I noted 256 volts while my kettle boiled. That warranted an email to powergrid pointing out ESQCR values. The current problems started after a fault on the area 11kV overhead line network resulted in switching around the problem. The somewhat duller days recently have alleviated the problem somewhat as the local mains voltage while out of tolerance hasn't quite created shut down of my inverter.

[Andy Burns]

They have a capacity map

Maybe that isn't fine-grained enough to see your substation, WPD seem to include down to street-level substations

[John J]

Thanks but it doesn't seem to show details of substations and distribution around my location. Apart from the sub I mentioned there's a pole mounted unit at the far end of my road which I believe supplies part of the loads towards me but there's a currently open circuit link box between the two ends of the road. Across the other side of the main road that bisects the village are a at least 3 other substations. I'm not sure how much of the opposite side is fed from them or if some of that area is fed from "my" substation. Pity the YEB is no more as I used to know a couple of their engineers. :-(

[tony sayer]

Telling them that it's out of voltage tolerance is like water off a ducks back in my experience!.

Especially of they have to spend any upgrade money!....