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Is my PV Inverter kaput or has a panel gone?


(Simon) #1

Hi,

It’s been clear locally for the last few days - think we’re having summer in February here in the UK!!

Given that, I’m a little worried by what our Solar PV is showing. I’ve copied a screen clip of the standard Solar dashboard on emoncms to show what I mean.

You can see a drop off which accelerates around 1pm which after about an hour suddenly jumps back to where I would expect it to be. Then later in the day there are smaller repeats of the same phenomenon.

I went back to last year in June and you can see a similar effect but the dip doesn’t go anywhere near as low and it quickly jumps back up.

My theory is that it is the inverter - which would be a shame as they are expensive. Mind you, we may be moving if we can get planning permission, so maybe we won’t do anything about it :wink: :slight_smile:

Here’s the clip - any thoughts anyone, anyone seen this before? And I was pressure washing the decking during the drop - which on a micro scale was quite annoying…


(Paul) #2

Do you have any other info for this timeline like AC voltage or inverter temperature?

Can you explain the usage activity? The blue seems to reflect the inverse of the solar generation , as the solar reduces the consumption increases. (or is the blue just import not consumption?)

If the temp or voltages are high, it maybe that the inverter is throttling until it cools or line voltage drops below ~250V. I have seen several cases of inverters “cutting out” but not so much “fading away”.

Does any part of each string get shaded at all? It looks like I would expect to see if the sun was moving around and a panel was gradually being shaded until the sun passed the point where the obstacle was in line. The repeat dips could be the same shade moving across other strings or smaller obstacles. The neighbours haven’t got scaffolding up or a tree/bush gotten overgrown? We have a neighbour that has a line of leylandii that used to give us occasional dropouts and fades at this time of year when the sun is low (until I took a chainsaw to them), they never caused and issue in the summer months and they were not a problem for the first couple of years after the PV was installed, but leylandii tends to grow real fast.


(Simon) #3

Hi paul,

Blue is consumption after taking solar off which is why it shows that inverse line as the inverter is throttling back.

There is a bit of shade that probably starts about the time of the start of the 1st drop on the very top corner of one of the panels but it never moves onto the other panels, so doesn’t explain the other dips later on.

I get the mains voltage from the emonTX but don’t have a feed on that - I guess I’ll have to get that going so I can see if there is any correlation.

Another weird thing thinking about it is that the panel at the other end to the one that’s getting a bit of shading around 12:30 is also in the shade in the mornings but there isn’t any similar throttling back until it moves into full sun.

Weird.

Simon