Voltage Spikes....

[Berneray]

Voltage spikes cause drops in solar PV performance | YouGen Blog | YouGen, Renewable Energy Made Easy

Interesting blog on this "phenomenon"....we came across it once after an install we did that included SolarEdge....the chap owned an electrical maintenance firm and had spotted it via the SE monitor...Luckily he bore with us.

We had to get the DNO involved...

 

[Gavin A]

from what I see on the forums, most of the time the relatively minor problems from grid issues are amplified massively by installers not setting the inverters to G83 properly, and not using the correct AC cable sizes, then trying to pass the buck.

Yes it dose happen sometimes that there are problems, but the DNO's usually sort it out fairly quickly if it actually is their fault. If it's not, then it's almost certainly down to one of the above 2 factors (or probably both).

fwiw, the SMA inverters do not flatline because of grid issues when in G83 mode, they trip out entirely or they work fully, no in between. They do derate like that due to the inverter being too hot, or if the installer has limited the inverter output, or installed a seriously undersized inverter, or there's shading on the system like a TV aerial shadow moving across it, or potentially if they've left them set to the new German standards that do derate like this at higher voltages.

So this really is a cautionary tale about checking that the company installing your system actually knows their stuff before signing on the dotted line, rather than grid voltage issues alone.

 

[Gavin A]

oh, actually I just realised this system is an east west split. Chances are that the installer hasn't used a dual MPPT inverter for it, or has used one, but only installed to one MPPT.

that's the sort of thing that would lead to a 50% reduction in output, not grid voltage spikes - well certainly not spikes that showed up as the output flatlining and not as the output dropping to zero for significant periods in the middle of the day.

 

[SolarCity]

This is exactly what I thought. If the inverter is cutting out due to voltage spikes and this actually resulting in a 50% drop in expected output then presumably the inverter would not be operating for 50% of the time - so not difficult at all to diagnose.

I'd be amazed if the problem is down to two orientated arrays being on one MPPT and SMA haven't managed to diagnose this issue either.

edit: Data logging shows flat lines on graphs but no error messages. Surely voltage spikes would show 'disturbance' error messages?