pv and wind turbine

[tombennetts]

Hi Guys

Did an install for a company yesterday, 18 x 200 watt panels with an omnic-4k-tl inverter wired in 2 strings, pretty much south facing. Got a call today as the inverter keeps cutting out. There is also a wind turbine onsite feeding into the same board (cant remember the power of the turbine at the moment) I turned the isolator for the PV off and measured my voltage, was getting 248.9 ac. I turned the wind turbine off and the inverter was running ok but as it was cloudy only got up to about 800 watts. When the wind turbine is running and the PV it shuts off before it gets to 800 watts. I'm thinking the problem is over voltage on the AC side once the inverter starts kicking out a decent amount of power. Anyone else have any ideas? The company I did the work for did not apply for permission to install the extra generation. I'm assuming that as the voltage is within western powers +10% tolerance its unlikely they would reduce it (at least not without charging a fortune!) Do different inverters have different tolerances for the AC voltage?

Sorry for the essay, and thanks in advance for any help.

 

[SolarCity]

Have you got the inverter set to G83?

I'm not familiar with that inverter so I'm not sure if they're generally factory set?

 

[tombennetts]

i assume its factory set as there is only one button and as far as i can tell all that does is scroll through the display, first time I have installed one as well!

 

[SolarCity]

Have you checked through the instructions? Does the inverter announce itself as being setup as G83 when you switch it on?

 

[babba]

http://www.electriciansforums.net/p...forum/52634-2-88kw-system-2-5kw-inverter.html

Have a look at this thread over voltage is discussed on this should help

 

[tombennetts]

thanks for that. went back today and it was sunny and not windy, PV was running fine so I'm sure thats it. Any one know what inverters have higher ac voltage tolerances?

 

[babba]

Try a power one 3.6 OUTD we had a similar problem with a sma 4000 tl changed it for a power one and no probs the sma was tripping out at 253v...

 

[Gavin A]

there shouldn't be much difference between any G83 inverters really - that's the point of G83, they're all basically the same unless you get permission from the DNO to alter the settings.

This is basically why you're supposed to get permission in advance to connect a PV system where there's already a wind turbine in place under G83/1 stage 2.

Essentially it sounds like the combination of the wind turbine plus solar PV system operating together when there's minimal load being drawn is trying to push too much power down the line, and the voltage is being pushed up above the 253V cut off point.

Unfortunately, I doubt you've got much chance of persuading the DNO that it's their fault, and that they need to adjust the tappings on the transformer as it sounds like the problem only happens when both the wind turbine and PV are running, and you didn't have permission to connect the PV on top of the turbine.

If I'm reading your opening post right, this is an SMA 4000TL inverter. If that's the case, you could try swapping the immersion heater for a 1 or 1.5kW version, then using the relay function on the inverter to trigger a contactor circuit for the immersion heater when the inverter output goes above something like 2.5kW. This would increase the load, and should reduce the voltage by a volt or 2, which may be enough to stop this being too much of a problem.

The other problem here is that when the appendix 3 form get's processed by the DNO they would be within their rights to turn round and demand the system is disconnected. I reckon it'd be worth raising this with the company at this stage to be sure that they understand where the liability lies here in case this does happen.


eta - oh, on second readings I see it's not an SMA inverter.

 

[Gavin A]

Try a power one 3.6 OUTD we had a similar problem with a sma 4000 tl changed it for a power one and no probs the sma was tripping out at 253v...

actually, I might have to stand corrected here.

I was under the impression that the 10 minute average 253V over voltage cut out on the SMA inverters was mandatory under G83 requirements, and that all G83 inverters ought to have the same settings.

After checking the G83 engineering recommendations, it seems that the only actual over voltage protection requirement specifically stated is for it to trip out at or before 264V.

From the power-one installation manual, it does seem like they've only got this higher over voltage cut out, so presumably wouldn't cut out in the way that the 4000TL does at 253V.

I'm not really sure though how Aurora get around the requirement for installation not to impair the quality of the supply, which I'm pretty sure does equate to the supply not going above a 10 minute average of 253V. If the inverter doesn't cut out when this happens, then the installation is helping to push the voltage out of the limits that the DNO is supposed to stick to, and is presumably would be classed as impairing the quality of the supply.

It's probably rarely going to be an issue, but it still seems odd to me that Aurora have obviously taken the view that they can ignore it entirely.

Long story short though, it looks like babba's right and the power one 3.6 OutD could well solve your immediate problems anyway.

 

[babba]

Only going on experience, power one seem to handle over voltage a lot better, I dont know why but the are a safer bet you dont seem to get as much hassle with the power one... like women they are a mistery...voodoo

 

[Gavin A]

I'm pretty sure the reason why is all in that post.

SMA set their inverters to cut out when the 10 minute average grid voltage goes over 253V, Aurora don't seem to have this protection setting.

So aurora's will perform better in situations where the grid voltage is likely to go over 253V regularly, but using them would also put you at risk (relatively low risk) of the DNO kicking off because your installation was pushing the local grid voltage up outside the voltage limits they're supposed to be sticking to.

Technically you could be liable for any problems that resulted from this, but I can't see this being a problem unless there were several installations on the same phase of a transformer all using the Aurora inverters.

I think I might ask Aurora's technical bods about this.

 

[Earthstore]

Also, any electrical appliance in the property will be running right up the top end of their limit, so may cause expensive equiptment to go pop as well.Still, you could end up with a daily job changing light bulbs for them too.Just as a thought, what is the incoming voltage with PV and turbine switched off?