Lightening

verdigoverdigo Solar Expert Posts: 428 ✭✭
Well I had been planning to do a little more for lightning protection this spring but I probably waited a little too long. Had a storm come through today while I was at work. My initial peak has at least three dead panels. One string is putting out around 13 volts another is putting out 40 volts while the remaining 4 strings look normal at about 80 volts. These are all strings of two 300 watt panels.

The Classic is screaming a loud repetitive beep and is showing a ground fault message. I disconnected the two bad strings at the combiner ground bus and çycled the DC main breaker and then turned the remains good PV strings back on.

Still getting the ground fault message so I removed the ground fault protection enabling jumper from the Classic's board. Still have the ground fault message.

Anyone with a MS Classic see this message before? Guess I will be checking out all the individual panels this weekend and reading the Clàssic manual.

Also took out everything in the house connected to the eathernet cable. Router, TV tuner and digital TV s.

Comments

  • Raj174Raj174 Solar Expert Posts: 795 ✭✭✭✭
    Have you checked the midnite forum for information on this? Might be helpful if you haven't.
    4480W PV, MNE175DR-TR, MN Classic 150, Outback Radian GS4048A, Mate3, 51.2V 360AH nominal LiFePO4, Kohler Pro 5.2E genset.
  • verdigoverdigo Solar Expert Posts: 428 ✭✭
    I have and also submitted a work order to midnite for some help.
  • DanS26DanS26 Solar Expert Posts: 247 ✭✭✭
    Tell us a little bit more about the grounding system you had prior to the strike.  It may help some people to understand or to evaluate their grounding structures.

    More than a single grounding point?   Cable guy sink a rod?  Cable entrance on opposite side of electrical service entrance?  Roof or ground mount and any auxiliary rods?

    i know its after the fact but you may be able to avoid future problems with a properly designed grounding system.
    23.16kW Kyocera panels; 2 Fronius 7.5kW inverters; Nyle hot water; Steffes ETS; Great Lakes RO; Generac 10kW w/ATS, TED Pro System monitoring with PVOutput.org
  • WaterWheelWaterWheel Registered Users Posts: 340 ✭✭✭
    While I can't help with the charge controller error I've got 4 MNSPD-300 (2 AC and 2 DC) in my grid tied battery backup system.       One of them is wired to the combiner box.

    We had a hell of a strike blowing out all of the neighbors electronics for 300 yards around the house (strike hit in my front yard).          All of the neighbors lost electronics like TV's and video games but I lost nothing except the items with separate grounds (satalite TV and electric fence).       Everything grounded to the house and panels was fine.

    Conext XW6848 with PDP, SCP, 80/600 controller, 60/150 controller and Conext battery monitor

    21 SW280 panels on Schletter ground mount

    48v Rolls 6CS 27P

  • verdigoverdigo Solar Expert Posts: 428 ✭✭
    edited April 2016 #6
    The solar shed that houses the batteries, charge controller, e-panel with inverter mounted to it, combiner box, and auto-transformer are grounded to a rod that is connected to the ground rod at the house. 

    In the picture below you can see panels mounted on the shed roof. That panel  sub array is grounded to the equipment ground rod that is connected to the ground rod at the house. The ones below that on the ground mount has it's own separate grounding rod for the frames. This is also the group of panels that were damaged. (You guys must be on to something here).  The panels closest in the pic did not have a frame ground yet and are un-damaged. 

    I had read some where that the PV DC negative and the frame grounding shouldn't be directly connected. I may have misunderstood.  Do you guys think I should ground all the panel frames to the same common ground for the solar system and the house?

    Thanks for your help.

    Dennis

    [URL=http://s1000.photobucket.com/user/verdigo59/media/shack done.jpg.html][IMG]http://i1000.photobucket.com/albums/af125/verdigo59/shack done.jpg[/IMG][/URL]
  • verdigoverdigo Solar Expert Posts: 428 ✭✭
    DanS26 said:
    Tell us a little bit more about the grounding system you had prior to the strike.  It may help some people to understand or to evaluate their grounding structure

    Your probably on to something here.

    All of the solar equipment is grounded to a rod at the solar shed which is connected to the grounding rod at the house except the one sub array, (A ground mount that is directly behind the shed which has four panels configured into two strings). This one has it's own ground rod for the panel frames and mounting rails. This is also the group of four panels that have lightning damage.  

    The panels on the shed roof frames and rails are grounded to the same common ground that the solar equipment and house are grounded to. The third group of four panel frames and rails on the ground mount closest in the picture had not been grounded yet but are un-damaged.




    Thanks for your help. I remember reading that the PV frames should not be grounded to the same ground that the PV negative uses.  


  • DanS26DanS26 Solar Expert Posts: 247 ✭✭✭
    Based on the information you have provided so far I do see a few issues, but there are a few pertinent facts we may never know.  Let's assume the strike was at or near the ground mount array structure.

    You have two rods at the array and they are NOT bonded together underground.  This will invite step potential voltage between those two rods if lightning strikes near the rods.  Here's what happens.....lightning does not strike the ground and travel straight into the earth, a common misconception.  Lightning will create a high voltage gradient in spoke fashion radiating out in a circular fashion.  Since the earth is high resistance the voltage will travel between rods through the less resistance above ground structure......ie your panels and inverters and other above ground equipment.  It appears that process caused your damage.

    IMO you have two choices...either remove one of those rods and bond everything at that site to that single point or bond the two (or more) rods together underground so that they stay at equal potential.

    Lastly the EGC (equipment grounding conductor) that connects to the home electrical grounding system should be the smallest wire that complies with NEC code.  The resistance in that wire length will resist voltage from entering the house for a long wire run....but no guarantees about that...lightning is very powerful.
    23.16kW Kyocera panels; 2 Fronius 7.5kW inverters; Nyle hot water; Steffes ETS; Great Lakes RO; Generac 10kW w/ATS, TED Pro System monitoring with PVOutput.org
  • zonebluezoneblue Solar Expert Posts: 1,218 ✭✭✭✭
    Its a common misconception that grounding the array frames helps protect them from lightning. It doesnt, and possibly has somethign of the opposite effect... like "Hit me". However for satefy reasons, the frames need to be bonded into the system's ground bus, as others have said using a light gauge conductor.  If you want to protect the array, then your best bet is a completely seperate grounded lightening tower.... ( i use our radio mast, hey after all the stuff up there doesnt belong to me ;) .... and SPDs. Lots of them.

    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


  • WaterWheelWaterWheel Registered Users Posts: 340 ✭✭✭
    Like Dan and Zoneblue already said and my local solar guy stressed you only want 1 ground.        My ground mount panels with the Midnight Solar surge protectors is ground through the house's ground rod. 

    Conext XW6848 with PDP, SCP, 80/600 controller, 60/150 controller and Conext battery monitor

    21 SW280 panels on Schletter ground mount

    48v Rolls 6CS 27P

  • DanS26DanS26 Solar Expert Posts: 247 ✭✭✭
    foolami said:
    Like Dan and Zoneblue already said and my local solar guy stressed you only want 1 ground.        My ground mount panels with the Midnight Solar surge protectors is ground through the house's ground rod. 
    Just food for thought......a lot depends on how far your ground mount is away from main service ground......then also if your ground mount foundation is galvanized pipe in concrete (ie UFER's) or if (like the OP) your mount is wood posts.


    23.16kW Kyocera panels; 2 Fronius 7.5kW inverters; Nyle hot water; Steffes ETS; Great Lakes RO; Generac 10kW w/ATS, TED Pro System monitoring with PVOutput.org
  • zonebluezoneblue Solar Expert Posts: 1,218 ✭✭✭✭
    edited April 2016 #12
    No ive recently changed my thinking on this. I was influenced by previous NEC iterations which vacillated on the topic of distant ground racks having their own stake and then not. The current thinking is that if you have a separate array stake it MUST be bonded to the main stake. But the reasoning explained above tends to mean that the array stake even if distant is redundant. If you must have a seperate stake attach it to a completely seperate galv mast positioned near the array. Hit me instead.

    The only valid reason for frame bonding is to cater for the fault event where an array hot shorts to frame presenting possibly high ELV voltages to unsuspecting users. If your array Voc is sub 20V then there is no need to bond it at all, and some good reasons not to as discussed above. Indeed many jurisdictions allow Voc of up to 50V before ground bonding is required, and its a matter of what you feel safe with. However for practical intents and purposes most of use running 2S and 3S 60 or 72cell off grid configurations and so bonding is a fact of life.
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


  • verdigoverdigo Solar Expert Posts: 428 ✭✭
    edited April 2016 #13
    Well. I have one 4 panel group that has it's own exclusive grounding rod with 3 of the 4 panels toasted. I have one set that is bonded to the system grounding rod which in turn is bonded to the house grounding rod with no damage. The third, (due to procrastination) has no separate ground for the frames and rails and also has no damage.  I am belief at this point is it may be better to leave them all ungrounded. My thinking is it may be better than bringing lightning into the house.

    Thoughts?
  • DanS26DanS26 Solar Expert Posts: 247 ✭✭✭
    My thinking has also changed over the years about lightning protection and the interface with electrical distribution systems.

    In the absence of a commercial lightning protection system, such as found in the communication industry, a direct strike will do as it pleases no matter how your home or solar system is grounded.  The physical properties of a direct strike are so overwhelming that an 8' ground rod is meaningless.

    Thus in a direct strike you are mostly powerless and can only hope it is diverted or deflected away from your valuable equipment.....but if the strike is nearby say a tall tree or POCO's power lines or you are subject to a less powerful side strike then you have a chance of mitigating the damage.  Here is where the NEC has stepped into the fray.  The single point grounding electrode is important since it mitigates the reemergence of electrical energy from below ground into above ground structures and devices in the event of a nearby strike.

    I take your question to be "Should I leave my remote ground mount array without an earth stake?"  IMO it should be staked (ie connected to earth at one point at the remote site) especially since it is mounted on wooden posts.  It is your best chance of directing a strike to earth in the shortest path possible.  I would also recommend placing high quality SPD's in and around your equipment.
    23.16kW Kyocera panels; 2 Fronius 7.5kW inverters; Nyle hot water; Steffes ETS; Great Lakes RO; Generac 10kW w/ATS, TED Pro System monitoring with PVOutput.org
  • zonebluezoneblue Solar Expert Posts: 1,218 ✭✭✭✭
    > am belief at this point is it may be better to leave them all ungrounded.

    Its important to understand the distinction between grounding and bonding. People tend to use these terms interchangeably, when that is incorrect. For some reading, theres some links at the top of one of my writeups: http://zoneblue.org/cms/page.php?view=system-earthing

    Basically bonding is tieing metal parts to your "ground" bus so that everything touchable is at the same potential (EGC). Grounding is connecting the "ground" bus to "earth" (GEC). Therefore if you have two metal frames with their own stakes, they are not at the same potential, because the earth between them is 25 ohms or greater. If you array voltage is non trivial then bonding is often required by code.


    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


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