Jump to content

DC-INTF fault (DC Interference)


Recommended Posts

I have a random DC interference fault occurring in my solar installation and none of the "professional" installers here in the Gansbaai area seem to be knowledgeable or have had any experience with a DC_INTF fault (Hopefully I am wrong): (I will not consult the original installer, he made a total mess, even installed the inverter to wrong height with the installation guide in his hand) I have been eliminating faults one after the other by myself for the past two and a half years with only the DC-INTF remaining)

My system is as follows:

Solis S5 6Kw inverter, 2x Hubble 5.12Kwh batteries, 17x 535W panels in 2 strings (8+7). There is a neutral bridge box installed. Refer to the attached photographs and the Solis fault sheet.

I have gone through absolutely every possible scenario on the fault sheet but the DC-INTF fault still occurs. My neighbour is a "normal" installer using a certified electrician to check his installations and provide his COC's. He is not an expert, but helped me eliminate all the other faults bar DC-INTF. I separated the DC cables from the AC cables so that they run in its own trays, we loosened all the panels and checked every single connection, we made sure every cable connection is screwed tight. I have read up everything I could find on faults in solar installations, but to no avail. The most frustrating is that the fault occurs randomly, and I am not able to pinpoint any common factors, having recorded each instance for few months still did not help. Now when it happens, I just switch the change-over switch to grid for some time and back to solar, but it does not solve the issue.

I hope there is someone out there that could point me in the right direction.

DB Boards_2.pdf DC-IINTF Fault check.pdf Inverter and batteries.pdf DB Boards_1.pdf

Link to comment
Share on other sites

The first challenge is the intermittent nature of the fault. All points to a dc fault but the question now what is causing the fault.

3 hours ago, andrevanschalkwyk said:

Now when it happens, I just switch the change-over switch to grid for some time and back to solar, but it does not solve the issue.

This is interesting, do i understand correctly does this clear the error just to happen again on a diffrent time? The way i understand the above explanation is you remove the load from the inverter and then power the loads via utility switch the load back to inverter. You don't switch the input of the inverter off you just cycle the transfer switch?

Is your panels earthed via a ground rod or/and connected to utility ground? Is your battery casing earthed? You do have comms between batteries and inverter? 

Link to comment
Share on other sites

4 hours ago, TaliaB said:

The first challenge is the intermittent nature of the fault. All points to a dc fault but the question now what is causing the fault.

This is interesting, do i understand correctly does this clear the error just to happen again on a diffrent time? The way i understand the above explanation is you remove the load from the inverter and then power the loads via utility switch the load back to inverter. You don't switch the input of the inverter off you just cycle the transfer switch?

Is your panels earthed via a ground rod or/and connected to utility ground? Is your battery casing earthed? You do have comms between batteries and inverter? 

Considering your response I believe we are on the right track as to the cause of the problem, i.e. that the panels are earthed to the main board/house earth and not an earth spike. The fault occurs randomly and not under any specific/identifiable conditions or time, for instance after correting an installation fault at times several weeks passed without any issues then flares up again. But let me go through the process that I followed to try and fix some of the installation errors leading up to where I am at now..


Most solar installations here are earthed to the home earth and not necessarily to a spike. However on advice from my neighbour I drove an earth spike and ran the wire through a window and changed the panels' earth to the spike to see if that solved the fault. This did not eliminate the problem and after some time it occurred again. Then I checked the earth neutral bridge box and found the wiring in the box was wrong. After consultation with Steve Fury I corrected the wiring nothing happened for some time, then the DC-INT fault popped up again, so I reverted the earth back to the house. Again nothing happened for a few weeks then the fault popped up again. Although the fault indicates that it should only be related to DC, I literally traced very wire between the Main DB, Change Over Switch and Earth Neutral and found incorrect routing which I then corrected 10 days ago, hoping that this could be the cause. However, in the last 4 days the fault occured 3 out those 4 days.
 

Having now fixed, as far as I can assess, all the main errors, all that remains is the earth of the panels to be connected to the spike again (I just have to drill through a 430mm thick wall). I just need to find day without rain. Hopefully this will solve the issue and I will update on the forum

Regarding your last questions, the battery casings and inverter are earthed and there is CAN comms between batteries and inverter

Link to comment
Share on other sites

8 hours ago, andrevanschalkwyk said:

. I just need to find day without rain

Does the faulty occur during rain or is it randomly. The reason i am asking should 1 of the pannels in the array have an internal fault or micro crack they tend to leak dc to ground that could be detected by the inverter via the earth connection. I wrote a procedure on the forum how my solar installation team check each and every panel before installing them. We have installed many many panels but have found on 2 occasions panels leaking dc to the frame. I will find my procedure and post it as soon as i get some time. Hope you find the problem in the meantime. If all avenues are exhausted you may have to get the inverter swapped out as it might be an internal dc fault in the inverter itself.

Link to comment
Share on other sites

As a means of trying to find the fault that is now nearly every day can you not just isolate 1 of the 2 strings at a time to see if it is possible to find which string causes the fault?

Link to comment
Share on other sites

2 hours ago, TaliaB said:

Does the faulty occur during rain or is it randomly. The reason i am asking should 1 of the pannels in the array have an internal fault or micro crack they tend to leak dc to ground that could be detected by the inverter via the earth connection. I wrote a procedure on the forum how my solar installation team check each and every panel before installing them. We have installed many many panels but have found on 2 occasions panels leaking dc to the frame. I will find my procedure and post it as soon as i get some time. Hope you find the problem in the meantime. If all avenues are exhausted you may have to get the inverter swapped out as it might be an internal dc fault in the inverter itself.

Thank you talia B. The fault is completely random, no common factors. Last year I thought it was the Inverter and had it swopped out, so that's not the cause. I will let you know how it goes after the earth has been corrected.

Link to comment
Share on other sites

2 hours ago, Scorp007 said:

As a means of trying to find the fault that is now nearly every day can you not just isolate 1 of the 2 strings at a time to see if it is possible to find which string causes the fault?

I have done that and it makes no difference. The problem is that at times it took a few weeks until it surfaced again, and once the inverter resets, it seldom replicated the fault. At this moment it seems to have gone away again. I believe will follow TaliaB's advice to connect the panles' to the erath spike and then monitor what happens

Link to comment
Share on other sites

Good day, I connetced the earth of the panels to the earth spike, but now I will have see if the fault rears its head again. Will probably have to give it about 2 weeks, today and the rest of this week is cloudy and rain almost every day.
I went through my data I recorded again and there appears to be some indication under which conditions the fault occurs. From what I observe it happens when the batteries are close to, or fully charged, and the PV generated is not sufficient to cover the power demand, and the inverter needs to distribute the power demand between PV and battery. It does not happen if the grid is off and I only run solar and batteries. I specifically checked this for 3 weeks switching the grid off in the morning and only back on again at sundown.The only thing then was that I did get AC Backup overload when too many appliances were running simultaneously. The geyser is also on my essentails, but fitted with a 2kW element.

Link to comment
Share on other sites

  • 3 weeks later...

After running through the wiring systematically again I found that the batteries were incorrected connected and that the 2 batteries were not equally charged. I fixed this today, both batteries then charged to 100%  but later had the DC-INTF problem again. Switched to grid to allow the Inverter to reset (about 3 minutes), then back to solar with the fault appearing almost immediately; again switch to grid, allow to reset, swith to solar to see it would agin rear its, but after that no issues. I will have to monitor the sytem again for a few days isnce we should have sun for the next 4-5 days.

If it happens again I have no idea what to look for.

PS: I am considering giving a full report of all the faulty installation issues to the Municipality since I had the system approved upon the COC from the original installer but I doubt if this would achive anything. It has however cost a lot up to now to fix all the errors.

Link to comment
Share on other sites

Hi @andrevanschalkwyk  , I can see that you have done a lot homework here , and probably left very little to the imagination. You have even swopped out inverters amongst other things.  I am not a Solis expert by any stretch , so I cannot contribute much .  All I want to add is that you disconnect all 4 dc surge protectors for a test period . This is of course only applicable if you have not done so already. If you have not , don't be shy to remove them , as Solis has already a Type II level of surge protection on its MPPT's input . Do not hold your breath that will fix your problem , but it cannot be ruled out that a faulty surge protection module can impose a substantial leakage to earth if it is not a quality type or if its rating is not suitable or if its from a bad production batch. Can you send us a higher resolution image of one of the surge protection modules, I take it that it is those red modules in your DC DB box.

 

21 hours ago, andrevanschalkwyk said:

PS: I am considering giving a full report of all the faulty installation issues to the Municipality since I had the system approved upon the COC from the original installer but I doubt if this would achive anything. It has however cost a lot up to now to fix all the errors.

If I am you , I would not waste my time with the Municipality ,they will just tell you that the DC domain is not their concern,  but rather compile a report and direct it towards Solis themselves. They do have field engineers that should be happy to investigate your problem.

Edited by BritishRacingGreen
Link to comment
Share on other sites

Hi @BritishracingGreen, thank you for your edvice. In the meantime I just found hopefully a last installaion fault. The batteries were connected wrong, instead of positive of the first batttery to Inverter and negative from the second to inverter, they were connected piggyback and then poitive and negative from battery 1 to inverter. I now fixed this and testing cherging 100% from grid for a few days, then I will let the system run normal to see if the fault rears its head again. What put me onto looking at the batteries was when I noticed that the system still showed 590W charge to the batteries while shoning the SOC as 100%. I believe the problem stems from the incorrect linking of the batteries, particularly since this problem did not show up until the last few months of last year. I would think that the inverter is "confused" (to put it in simple terms) from which source to provide power whilst the backup source is still charging at 100%. Battery 1 has probably been compromised over time and is now taking longer to fully charge and get to the state where the batteries are balanced. It will most likely take a few weeks to fully test to get a reuslt since we are having cloud cover for the whole of this week.
The list of issues I had and found with the installation is an absolute disgrace to reputation of the installer who was supposedly an expert and highly recommended. I am not an electrician, but in the process I have learnt enough and have vowed that, if I have to move and have solar agiain, I will only have the panels installed by an outside party, but everything else I will do myself and then get someone to check and provide the COC.
 

Link to comment
Share on other sites

On 2024/06/20 at 5:52 PM, BritishRacingGreen said:

Hi @andrevanschalkwyk  , I can see that you have done a lot homework here , and probably left very little to the imagination. You have even swopped out inverters amongst other things.  I am not a Solis expert by any stretch , so I cannot contribute much .  All I want to add is that you disconnect all 4 dc surge protectors for a test period . This is of course only applicable if you have not done so already. If you have not , don't be shy to remove them , as Solis has already a Type II level of surge protection on its MPPT's input . Do not hold your breath that will fix your problem , but it cannot be ruled out that a faulty surge protection module can impose a substantial leakage to earth if it is not a quality type or if its rating is not suitable or if its from a bad production batch. Can you send us a higher resolution image of one of the surge protection modules, I take it that it is those red modules in your DC DB box.

 

If I am you , I would not waste my time with the Municipality ,they will just tell you that the DC domain is not their concern,  but rather compile a report and direct it towards Solis themselves. They do have field engineers that should be happy to investigate your problem.

Here is the picture of the surge protectors

20240626_123253-Copy.jpg

Link to comment
Share on other sites

1 hour ago, andrevanschalkwyk said:

Here is the picture of the surge protectors

20240626_123253-Copy.jpg

I am speculating on my next suggestion but seems you have exhausted your options. It could be possible unlikely but possible that one of the dc spd is leaking a small amount of current to earth and maybe detected by the inverter. What you can do is to disconnect the earth wires from the spd's at the bottom and then test the system for a few days to see if it clears the dc leakage detected by die inverter. Make sure not to follow my advice if there is clouds or rainy weather just in case of a ground lightning strike that would leave your system vulnerable. Or the safe option would be to replace them that could mean you might end up with spare SPD's.

Edited by TaliaB
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...