Burnt out Cable Connection on 100kW inverter | on ElectriciansForums
Click here to remove these ads

Burnt out Cable Connection on 100kW inverter

Post new thread

Discuss Burnt out Cable Connection on 100kW inverter in the UK Electrical Forum area at ElectriciansForums.net

R

RCherry

Joined
Jun 24, 2022
Messages
10
Reaction score
2
Location
South africa
Hoping someone can give some input on what could be possible causes of what happened here. I am going to investigate the situation next week but for the time being I am trying to get as much input as possible to possible causes .

The install consists of 7x 100kW Huawei Grid Tied Inverters ,the system has been running smoothly for the past 9 months, faults came through on the monitoring platform and when an technician was sent out this is what was found .

My first and quite frankly only reasonable explanation is a loose connection ,but ,to the best of my knowledge a loose connection would have burnt out locally (at the point of termination where cable was loose ) . But in these pictures the cable is burnt out both at the inverter and then all the way back to the circuit breaker in the distribution board .

Any other ideas would be greatly appreciated and if my thinking about "localised" damage is incorrect if someone could explain otherwise that would also be greatly appreciated.
 

Attachments

  • [ElectriciansForums.net] Burnt out Cable Connection on 100kW inverter
    IMG-20220624-WA0131.jpg
    104.3 KB · Views: 83
  • [ElectriciansForums.net] Burnt out Cable Connection on 100kW inverter
    IMG-20220624-WA0130.jpg
    79.1 KB · Views: 78
  • VID-20220624-WA0133.mp4
    2.3 MB
  • [ElectriciansForums.net] Burnt out Cable Connection on 100kW inverter
    IMG-20220624-WA0124.jpg
    139.6 KB · Views: 70
Sort by date Sort by votes
A sustained overcurrent could cause the damage you are seeing.
 
Upvote 0 Downvote
Just watched the vid again, I think you are right, there is some shiny stuff there possibly from arcing between the 2 terminals.
I wonder if there is any animal parts that have been well cooked between the terminals that started an arc going?
 
Upvote 0 Downvote
So the 'apparent' short is at the inverter and your fourth image is the mccb. To me a short has occurred at the inverter and tripped the mccb with the conductors contaminated by vaporized copper exhausted by the mccb.
 
Upvote 0 Downvote
Well ,I say sealed but what I mean by that is sealed from natural elements . Also very unlikely that someone tampered with it because only 3 people have keys to the inverter location and it would be in none of their best interests to even enter the cage for any reason other than if there was a problem. I guess I will hopefully find my answer when I go investigate for myself during the week
 
Upvote 0 Downvote
If there was negligence on one of my guys behalf when it was initially installed last year and the terminal was not torqued ( unlikely because I check and then then the installation undergoes quality checks by a 3rd party) but if it was loose connection would there not at least been a minimum been a considerable voltage drop ? In which case the inverter would have pushed warnings a long time ago
 
Upvote 0 Downvote
If these are grid tied inverters then you have the other issue of grid generated fault current if there has been a breakdown of the phase barriers in the inverter. We have had some great weather recently and it possible the inverter could have initially generated thermal damage through solar action and the grid has finished it off.

Total guess of course, what really matters is who pays for all that damage.... eek
 
Upvote 0 Downvote
plugsandsparks said:
If these are grid tied inverters then you have the other issue of grid generated fault current if there has been a breakdown of the phase barriers in the inverter. We have had some great weather recently and it possible the inverter could have initially generated thermal damage through solar action and the grid has finished it off.

Total guess of course, what really matters is who pays for all that damage.... eek
Click to expand...
Even if they were not grid ted and working in their own island, there are several of them so the others could gang up on a faulty one and finish it off in much the same way as the grid would.
 
Upvote 0 Downvote
Correctly connecting al and cu | Klauke - https://www.klauke.com/gb/en/correctly-connecting-al-and-cu

https://solar.huawei.com/en/download?p=/-/media/Solar/attachment/pdf/au/service/Supporting/SUN2000/SUN2000-100-125KTL-Series-UserManual.pdf

I would thoroughly check the way the aluminium cored power cable has been terminated to the inverter copper connections OT/DT. See section 5.6 of the second reference which is the installation manual for the inverter. The first reference is a brief introduction to the problem of galvanic corrosion between aluminium and copper surfaces as in a bolted connection and the employment of transition terminations to ensure corrosion does not happen.

I think the yellow line connections at the inverter has over time failed through galvanic corrosion and become more resistive leading to significant ohmic heating, carbonisation of surrounding plastic and surface tracking between yellow and blue lines (and some visible also between red and yellow). Surface tracking has caused more ohmic heating and R to Y and Y to B line to line currents additional to the normal peak 100kW circa 150A inverter output line currents especially in the yellow line.

Eventually an arc has occurred between yellow and blue lines which has allowed such a high current to flow that the mccb has tripped. What you see as heat stress at the mccb yellow and blue terminals is because they have operated beyond their rated current and become too hot again through ohmic heating. Given more time I expect there would have soon been an arc fault between red and yellow well as between yellow and blue at the inverter terminals.
 
Last edited:
Upvote 0 Downvote
RCherry said:
@westward10 I actually accidentally posted the video thinking it was the picture ,it is the termination points at the inverter itselfView attachment 98791
Click to expand...

marconi said:
Correctly connecting al and cu | Klauke - https://www.klauke.com/gb/en/correctly-connecting-al-and-cu

https://solar.huawei.com/en/download?p=/-/media/Solar/attachment/pdf/au/service/Supporting/SUN2000/SUN2000-100-125KTL-Series-UserManual.pdf

I would thoroughly check the way the aluminium cored power cable has been terminated to the inverter copper connections OT/DT. See section 5.6 of the second reference which is the installation manual for the inverter. The first reference is a brief introduction to the problem of galvanic corrosion between aluminium and copper surfaces as in a bolted connection and the employment of transition terminations to ensure corrosion does not happen.

I think the yellow line connections at the inverter has over time failed through galvanic corrosion and become more resistive leading to significant ohmic heating, carbonisation of surrounding plastic and surface tracking between yellow and blue lines (and some visible also between red and yellow). Surface tracking has caused more ohmic heating and R to Y and Y to B line to line currents additional to the normal peak 100kW circa 150A inverter output line currents especially in the yellow line.

Eventually an arc has occurred between yellow and blue lines which has allowed such a high current to flow that the mccb has tripped. What you see as heat stress at the mccb yellow and blue terminals is because they have operated beyond their rated current and become too hot again through ohmic heating. Given more time I expect there would have soon been an arc fault between red and yellow well as between yellow and blue at the inverter terminals.
Click to expand...
I appreciate your input but the conductor and the lugs used are copper
 
Upvote 0 Downvote
Undaunted……

I suspect then the output power stage, the output and EMI filters, the contactor or the ac surge protection device all of which connect across the lines, neutral and to earth. See section 2.5.1

What I would do is turn off and isolate two good inverters and after allowing time for capacitors to discharge take a low voltage ohmmeter and measure the resistances between all possible pairs of lines, neutral and earth. It takes 15 minutes before a de-energised inverter is safe to touch.

Then do the same for the damaged inverter and compare with the two good inverters. If the inverter is damaged internally you will see differences in resistance measurements. Armed with this information you can contact the supplier/manufacturer and discuss what has failed and warranty/ guarantee replacement.

Please resist the temptation to open up the damaged inverter because you will likely void the warranty/guarantee. (This is what happened to a French farmer I helped with his solar system problem. If he had not opened up the inverter it would have been replaced gratis but he was too curious not to have a gander to see if he could repair it himself).

ps: when doing r measurements do both polarities.
 
Last edited:
Upvote 0 Downvote
I recommend you check the software settings for grid connection. See Section 7.1.5.1 Grid Parameters and 7.1.5.2 Grid Protection Parameters.

Did you log any fault messages? Or did the inverter continue to provide power to the grid until the mcb tripped?

Did the inverter trip during a period of solar electricity generation or at night when it was either in standby or if selected generating and exporting reactive power?

I’d measure the line to line, line to neutral, line to earth and neutral to earth voltages.

what is the earthing system please?

is the internal cooling fan functioning well?
 
Last edited:
Upvote 0 Downvote

Reply to Burnt out Cable Connection on 100kW inverter in the UK Electrical Forum area at ElectriciansForums.net

Similar Threads

R
  • Question
NVQ Portfolio Help Unit 115 - Fault Finding
Great, then I am a bit bemused why you posted your original question. You need to stop doing any work that you cannot properly test, safety is...
Replies
12
Views
785
PS Electrics
PS Electrics
C
  • Question
Cooker and kitchen power cables to be enclosed in rockwall
Hello oscar21, When I wrote about cables heating up I meant that IF a cable heated up that heat could not dissipate correctly if the cable was...
Replies
16
Views
2K
chris murphy
C
B
  • Question
UK RCD Protecting Distribution Cables on a TT on Industrial Estate
much more information required. Is the supply to the first building a DNO supply or a sub main cable from another building ? if it is a sub main...
Replies
5
Views
832
MDJ
MDJ
J
  • Question
UK second solar pv inverter and batteries?
Hi all. We have had 7x 400w solar panels for a number of years now on our roof which is se/nw facing end terrace. 4 on se side 3 on nw side...
Replies
0
Views
1K
john boileau
J
1
  • Question
Help Understanding EICR
I suspect that the Wylex metal CU was put in during the 1978 work, perhaps along with the majority of the wiring, and rather less was done in the...
2
Replies
29
Views
4K
Lucien Nunes
Lucien Nunes

OFFICIAL SPONSORS

Electrical Goods - Electrical Tools - Brand Names Electrician Courses Green Electrical Goods PCB Way Electrical Goods - Electrical Tools - Brand Names Pushfit Wire Connectors Electric Underfloor Heating Electrician Courses
These Official Forum Sponsors May Provide Discounts to Regular Forum Members - If you would like to sponsor us then CLICK HERE and post a thread with who you are, and we'll send you some stats etc

YOUR Unread Posts

Tilers Community
This website was designed, optimised and is hosted by untold.media Operating under the name Untold Media since 2001.
NHS Forums | Forum for NHS Staff and NHS Patients
Back
Top
✖
AdBlock Detected

We get it, advertisements are annoying!

Sure, ad-blocking software does a great job at blocking ads, but it also blocks useful features of our website. For the best site experience please disable your AdBlocker.

I've Disabled AdBlock    No Thanks