DNO turning off systemsDno turning off systems

[tottenham steve]

Having discussed the event codes with SMA, they are saying that the disconnections are caused by high grid impedence caused by an initial high grid voltage

 

[tottenham steve]

Sorry to ask again, but how many properties does the DNO supply from the transformer?

Sorry, I dont know, but its quite rural , i would guess at less than 20

 

[Earthstore]

This is my understanding here.
If all 20 houses are pulling a base load from the grid of 0.5KW, than that would use all of your 10KW produced, therefore, not pulling any from the transformer, so the voltage in the grid would stay at 251v, however, if your PV power has nowhere to go, it would then push the grid voltage up causing your problem.

My question was; what is your incoming voltage reading when your inverters say it is 290v, you need to make certain that it not an install fault, as the DNO will not get involved in that.

Do any of the other 20 houses have PV?

 

[Gavin A]

If I stick to those limits the system will disconnect, How is the system supposed to work?

I think you're in trouble then, and the DNO has obviously made a mistake in giving you permission to connect 10kW on to that line.

The problem is that if they've put their testers on the line while your system is conencted like this, it'll clearly show your system pushing the voltage up above the limits because of the changes you've made.

If the local voltage is that high, I'd think the best course of action would be to ask them to test it again for 2 weeks with your system switched off, then hope that in these 2 weeks the local grid voltage goes outside the limits anyway, then they will have to reduce the tapping on the transformer.

Explain to them that you will then reset the inverters protection settings to stay within the 253V 10 min average, and 264V instantaneous limits, and there should then be no problem.

Whatever you do, I'd try to keep the engineers on side, and defo not kick off with them as you're on very dodgy ground here, and they'd be within their rights to cut the power supply off entirely if you simply left it as is.

 

[Avontech]

We had a recent discussion with one DNO about grid voltage's as we had one system cosistently disconnecting with high grid voltages, and it seems that they've recently turned them up in rural areas !! After a very polite conversation they volunteered (without even asking) to retap the local transformer and turn the voltage down.

Speak nicely and you'll be suprised what co-operation you can get!

 

[TedM]

I have advised on one recent very similar case (but only 4kW) where the DNO were insisting that the PV was at fault.

The DNO provided graphs of their monitoring and upon examination it was clear that grid voltage was going too high at times when the PV simply couldn't be affecting it - like the middle of the night or very early morning. If they have already monitored your supply then ask to see the results. In this case the DNO were just trying it on and rapidly backed down and re-configured the transformer.

They are within their rights under the ESQCRs (section 34) to request removal or switch you off if you are causing the problem. They cannot just disconnect you though - they have to serve you with a notice. You then have to comply as an interim measure but can dispute the notice and get the issue handled independently.

(Said it before - voltage test should be part of any initial site survey. Any highish figures (>250V) should trigger a request to the DNO to monitor before even installing the PV.)

 

[SolarCity]

Lesson learnt. I was under the impression that any issue caused by a correctly installed PV system was the responsibility of the DNO and that they should lower the grid voltage.

 

[jupestar]

This is a really good post. why I like this forum Will be interested to hear the final outcome.

The fact they can order disconnection is pretty scary. Didn't know thatr. I feel a slight change about to be made to our T&C's...

 

[lancemoto]

Oh Dear!! I can see a big bust up with our DNO as they agreed for our 45kw to be connected because of low volts issues (300m overhead linesout in the sticks) they have agreed to upgrade the Overhead lines and even the transformer once they have planning permission and way leaves to re string the overhead lines.
The DNO did say when the PV is connected we may incur highvolt problems which they are correct is we Struggle to keep all the inverters on without using lots of different loads connected to each Phase.

I wait for the DNO to carry out their works and hope the inverters then all stay on Fingers crossed!!

 

[SolarCity]

Okay, what about if a system is installed and the grid voltage seems fine. And then the neighbours get systems installed. This would presumably have an effect on the grid voltage. Could the DNO really ask someone to turn their PV system off? Whose responsibility would this be?

 

[sedgy34]

We fitted a 10kw system a few months ago, G59 approval was granted prior to installation and all was carried out correctly.
unfortunatly there is high voltage in the area so the inverters were tripping at peak generation. We have recalibrated the inverters but still have a problem.
so we have asked the DNO to look at there transformer and after investigation they have concluded that our system is causing the transformer voltage to rise above there upper tolerance and ordered the system to be shut down, leaving me £30,000 out of pocket. Has any one else had the same experience?

i would be looking at voltage optimisation to see if that would help the over voltage,gonna be alot cheaper

 

[Gavin A]

i would be looking at voltage optimisation to see if that would help the over voltage,gonna be alot cheaper

I didn't think you could use VO's in that way - to feed power back to the grid through them.

 

[TedM]

Okay, what about if a system is installed and the grid voltage seems fine. And then the neighbours get systems installed. This would presumably have an effect on the grid voltage. Could the DNO really ask someone to turn their PV system off? Whose responsibility would this be?

This is where it starts to get a little tricky. I think if everyone involved has followed all the correct G83/G59 procedures then it would be down to the DNO to sort it out.

G83/2 makes the pre-notification position around multiple installations in a geographic region a little clearer, although it is still not totally unambiguous. I'm hoping that the covering guidance will resolve such things though.

 

[johnpoleman]

I worked as an engineer for a DNO for thirty-five years. Last year I had a 3.12kW system installed. All worked fine until mid summer when I noticed several trips taking place around lunchtime at peak production. I still had a calibrated voltage tester and my incoming volts with pv off production was around 250-252volts. I rang the local office as a customer and explained I wanted the situation logging. I actually knew that we had a 33/11kv primary transformer out for some work and the tap changer was on fixed tap due to a problem. This situation went on for about a week with tripping at peak production times when the DNO network was restored the problem still caried on.

I again contacted the DNO and this time explained the situation 'officially' Needless to say the lads that came round knew me and they admitted they knew very little about the voltage issues regarding PV production. They checked volts at the local sub-station (252v) and again at my house again just about on limits. We had a bit of a training session, tea, biscuits and a chat and they agreed volts were a bit high.
Next day they backfed sub-station lowered the tap and house volts incoming are now 240v with PV off.
All I can say to help is offer tea, biscuits and explain your point honestly. I understand they are flooded with these type of issues now, so I think I was lucky. I have no doubt they are now sticking to the terms and conditions to save money on network reinforcement.

 

[moggy1968]

Okay, what about if a system is installed and the grid voltage seems fine. And then the neighbours get systems installed. This would presumably have an effect on the grid voltage. Could the DNO really ask someone to turn their PV system off? Whose responsibility would this be?

Thats why, even under G83, you are required to notify the DNO if there are multiple installations in the same area. How many do? none I suspect, so stand by!