Burnt out Cable Connection on 100kW inverter

[RCherry]

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.

 

[westward10]

It looks like a dead short has taken place had the breaker tripped.
@Lucien Nunes may have a more scientific response.

 

[James]

A sustained overcurrent could cause the damage you are seeing.

 

[westward10]

A sustained overcurrent could cause the damage you are seeing.

Looks like a short between the two middle conductors on the video image although it isn't too clear.

 

[James]

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?

 

[RCherry]

It looks like a dead short has taken place had the breaker tripped.
@Lucien Nunes may have a more scientific responses

 

[RCherry]

That would be the most logical explanation to me although both the inverter and db is sealed and locked

 

[westward10]

@RCherry how does the video relate to those pictures.

 

[RCherry]

@westward10 I actually accidentally posted the video thinking it was the picture ,it is the termination points at the inverter itself

 

[westward10]

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.

 

[RCherry]

@westward10 thank you this is actually he most logical suggestion I've received. Now I just need to figure out how a short could have possibly occurred inside a sealed enclosure

 

[westward10]

Maybe you are not getting the full story, how was it sealed because if you have accessed it then why couldn't someone else.

 

[RCherry]

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

 

[James]

Have you looked in the other inverters to see if there is a build up of conductive dust?

 

[RCherry]

It wasn't me that went to the site, it was the funders site representative that went to check the site out ,I was made aware of this after he had left the site and sent the pictures (I am the installation contractor)

 

[RCherry]

The mccb did trip. I will take some pictures of the other inverters connections and post them

 

[westward10]

That pic in #9 does look like overheating from the spread down the yellow conductor but there also looks like a short. Someone tried to tighten it and ....................

 

[RCherry]

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

 

[westward10]

I'm no expert on solar inverters so I can't really comment.

 

[plugsandsparks]

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