Capacitor Bank Burst Issues

There is not enough information about the installation to warrant much more than a SWAG (Stupid Wild A$$ed Guess) but it sure looks like your installation experienced a severe transient overvoltage due to a resonant condition between your capacitor bank and the nearby inductive loads. Or the lightning /surge arresters were operating near their MCOV (Maximum Continuous Operating Voltage) when a lightning stroke/switching transient came along and pushed everything over the withstand level resulting in lots of ionization with subsequent flashover.

It's a great example of what happens when handbook engineers spec something based only upon the normal (easy) parameters like operating voltage/current, and don't account for the subtleties of what they're cobbling together.

Now how about giving us enough information to make an educated guess?

Your "loose connection" may have vaporized.

A thorough accident investigation may not be possible if you do not have a record of the system health immediately before and during the incident.

Inspection of burn patterns, the extent of damage to each component, spatter, and various other items will lead you to the root cause if you spend enough time on it.

How long was this arrangement in operation before the incident?

What did your electrical contractor say?

"Bloody hell!"?

Overheated joint that failed catastrophically perhaps. It's very hard to say with so little information provided.

How long has this equipment been in service and was it maintained?

Is there any other damage in the equipment or the overall plant itself other than the failed joint?

The basics of this thread are way to vague to comment on.

But I like this tangential issue...

• "... SWAG (Stupid Wild A$$ed Guess)..."

I have always taken SWAG to mean SCIENTIFIC Wild Ass Guess. The difference is... SCIENCE!

There are many variants: simple, simply a, silly, such a, seriously, serendipitous, etc. I chose "stupid" because OP expected an answer without providing any details.

A quick look at those pictures indicates a catastrophic failure of the system controlling the capacitors, one can infer from the title that the capacitors didn't look any better, and I wonder if the bank was fused and/or the caps had any discharge resistors. There was a lot of energy expended in a very short period of time.

sophisticated

Feedback? OK. You need to rip the whole lot out and replace it. There's no way I would mess with any of that.

What type of equipment's or load that is connected to this distribution board and if it is motor load, what type starter do you use...? Frequency inverter starter or other electronic devices to use to start the motor...

maybe: Capacitors operated out of their "safety zone" and overheated, maybe due to resoanance?