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Drops in solar production

Discussion in 'Tesla Energy' started by Shygar, Jul 23, 2018.

  1. Shygar

    Shygar Member

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    I've been noticing that I get these drops in my solar production. I'm guessing the inverter is getting hot and dropping everything for a short period. Any insights into this and if I should do anything about it? I also used to get the max 6.6 kW but lately it's been less, unless a cloud goes over then you can see it spike up briefly over 5.8 then back down.

    Screenshot_20180723-144226_Tesla.jpg
     
  2. miimura

    miimura Active Member

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    Could the drops be from clouds? We have had some tropical moisture passing by the Bay Area.
     
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  3. BerTX

    BerTX Active Member

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    By "drop" do you mean it stops completely or just dips below what you had previously noticed?

    The production from the cells decreases with heat, so you may be seeing that (particularly on roof-mounted systems where there is often less air circulation under the panels) -- you would think that production would be best in the summer and it is, but only because the days are longer so you get more production time. If you are looking at peaks, then those will be on cool to cold sunny days, not hot summer days.

    If you are getting complete cutouts, then it could be an inverter issue, or the inverter may simply be undersized. Just guessing here, as I have not had either of those issues.
     
  4. Jeffgtx

    Jeffgtx Member

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    yea, that looks like clouds going by.
     
  5. Shygar

    Shygar Member

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    That is my guess too, and since I'm at work in San Ramon I can't confirm if it was or wasn't a cloud, but I had another one of these drops the other day and it measured a flat zero according to the tesla app, then shot right back up. Even with clouds on a sunny day it should show some production. I just realized I can look back at my Nest Hello and see since it does 24/7 continuous recording:

    No clouds

    So I'm pretty confident there isn't a cloud in this scenario. This clip was from 12:30 to 2:30 today and the dips happened at 1:25 and 2:10.
     
  6. GenSao

    GenSao Member

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    I live relatively close to Shycar. No clouds and my App does not show any dips in solar production for my system.
     
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  7. wwhitney

    wwhitney Member

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    Is it producing nothing for 5 minutes? That could be the grid moving outside the inverter's operational window, and the inverter taking 5 minutes to resync to the grid.

    Cheers, Wayne
     
  8. Shygar

    Shygar Member

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    Hmm, I'm not sure I completely understand. I get it that it can resync and that does take time. But at least according to the app it wasn't a complete drop today (although in the past I have seen these drops go straight to zero). But what exactly is the inverter's operational window?
     
  9. cwied

    cwied Member

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    It may not be the same thing as what you're experiencing, but I saw weird dropouts like this for several days:
    upload_2018-7-23_16-30-53.png

    On the third day, the power went out for 11 hours. Apparently a construction crew nearby managed to do something to a utility pole that destroyed the transformer (perhaps caused it to catch on fire). Judging by fresh cuts to trees nearby, I wouldn't be surprised if some branches were shorting out the power lines. I was away on vacation at the time, so didn't actually see what happened.
     
  10. wwhitney

    wwhitney Member

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    Per your pvoutput.org link, it was a complete drop today.

    The grid tie inverter expects the grid to be within certain parameters. E.g. if it is nominally 240V and 60Hz, then maybe it requires it it be to 230V to 250V and 59 Hz to 61 Hz (those aren't the right numbers, I just made them up, you can look up the actual parameters somewhere). So if the grid momentarily goes to 251V, the inverter will disconnect and stop producing. Then the UL protocol on grid tie inverters (I forget the number, you can look it up) specifies that the inverter should wait a certain period of time before resuming production (I believe it is 5 minutes).

    And this issue of excess grid voltage does sometimes occur. It can be related to the size of the conductors connecting the inverter to your service disconnect. When the inverter is trying to export power, it raises its output voltage as required to just exceed the grid voltage and push out power (that's probably not quite technically correct, but that is the extent of my understanding). So what would normally be "voltage drop" due to the resistance of the wires between the inverter and the grid shows up as a "voltage rise" at the inverter. Thus if the grid itself drifts upward, it can cause the voltage at the inverter to exceed the maximum of the inverter's operational window.

    So the upshot is that if the drop outs are always at least 5 minutes, it can be due to grid hiccups, and if the drop outs always occur during periods of high power output, it can be due to voltage rise.

    Cheers, Wayne
     
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  11. Shygar

    Shygar Member

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    Thanks Wayne that makes sense! I do see PG&E has been working the next street over, which hopefully means they're working on the transformer related to me as they said a year ago they were going to upgrade it. But what is surprising is that @GenSao isn't seeing the issue as he's very close to me, and also if you look at my pvoutput I have another system that is also just 1 street away and it also didn't have the issue. I would think something like voltage dropping would be affecting the whole neighborhood.
     
  12. wwhitney

    wwhitney Member

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    Voltage rise from the service point to the inverter is specific to your site, depending on the size of your wiring and the current your inverter is producing. So a neighborhood slight voltage rise could bump your system outside the operational window if your site-specific voltage rise is on the high end. [Occasionally the cause of site specific voltage rise can be a mediocre connection somewhere between the service point and the inverter, causing extra resistance.]

    Anyway, the usual utility reconnection timer is 5 minutes, so the thing to check is whether the inverter production goes to zero for 5 minutes or more. Does the inverter have any logs that you could check to see if the grid voltage it sees is spiking?

    Cheers, Wayne
     
  13. Shygar

    Shygar Member

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    Hmm good question. It's a Delta Solvia 6.6 installed last year. I'll have to look and see if there's any kind of log I can get from it. Thanks for the detailed info!
     
  14. Shygar

    Shygar Member

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    So now it seems to be happening every day at almost the exact same time. At what point do I need to either check with PG&E or Tesla on this to see if there is a bigger issue? I do see PG&E trucks still working on some stuff on the next street over, so I'll wait until all that appears to be done. But it's just odd that it's happening at almost the exact same time 3 days in a row.

    Screenshot_20180725-134632_Tesla.jpg Screenshot_20180725-134638_Tesla.jpg
     
  15. wwhitney

    wwhitney Member

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    The data on your pvoutput.org looks to me to be consistent with the inverter dropping out, although it is not definitive. To troubleshoot that possibility:

    If you have a Kill-A-Watt or other means to safely monitor voltage at a receptacle at your house (the service would be a better point, but harder/less safe, and a lightly used branch circuit should be very close), and someone is around at the time of the drop (since you say the timing is somewhat predictable), you could see if the grid voltage is rising just before the the solar production drop out. Of course, it might be a momentary spike that doesn't last long enough for your meter to pick up.

    Obviously a recording meter would be a better solution, but I'm not aware if such a thing is available inexpensively.

    Cheers, Wayne
     
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  16. cwied

    cwied Member

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    FWIW, the Powerwall reports voltage. I don't know if there's an easy to set up logger that will let you see the voltage. I'm using pvoutput, but it only has one voltage channel by default (which usually shows the pv voltage) and is not that easy to set up.
     
  17. nwdiver

    nwdiver Active Member

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    Does your inverter record disturbances? A friends system gets a 'DI converter fault' about once a day. The inverter shutsdown very briefly than starts up again. Super-weird... it's been occurring for >4 years... still trying to figure out why.
     
  18. Shygar

    Shygar Member

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    Hmm not really sure. I haven't had a chance to figure out how to check the logging of the inverter. It happened again today at 1:40 PDT. That's 4 days in a row.
     
  19. Shygar

    Shygar Member

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    FYI I called Tesla powerwall support and they confirmed seeing the issue (although they said they were surprised they didn't catch it first). They are sending a tech out next week to look at my inverter.
     
  20. Shygar

    Shygar Member

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    Tech came out, suggested a firmware update to my Delta inverter. I saw it was pushed a couple of hours later. Gonna keep an eye on it to see if it helps.
     
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