3 phase surge on reenergising panel board

[bigspark17]

Hi all..
Bit of a nightmare afternoon,, testing a caravan park TP&N panel board IR testing while board isolated before returning power (merlin gerin panel board) over the next 30 mins customers on park are reporting loud bangs inside some of there vans, boilers and electric fireplaces (with pcbs) exploding..

Wondering if any1 else experienced similar or shed some light on this..
Seems to me like it could be a temporary loss on Neutral somewhere be it a downstream fault in cable, loose neutral or dodgy main switch (was 4 pole) if the neutral lost on 3 phase with then single phase circuit voltage rising to 400v+ would have caused this pcb problems..

Appreciate and info

 

[James]

i think you are right on the cause, loss of neutral whilst 2 or more phases are connected.

If it was the IR testing that damaged things, i would expect delicate electronics to fail but not in a loud bang type of way.

map out the damage by phase and distribution board, the fault must be upstream of them all and probably downstream of everything that has had no faults on attached circuits.

 

[Darkwood]

Typical result of neutral loss, the remaining phases use anything that was connected to neutral as a alternative path yet much higher voltage, the main neutral bar becomes a star point of the phases and loads connected allow the voltage rise often destroying delicate circuitry.

 

[davesparks]

I've heard about this happening when someone doing testing forgot to reconnect the neutral disconnection link before re-energising.

 

[Marvo]

Yup, definately sounds like more than one phase energised and no neutral. Did you do any tests after the event or did you just run away before the pitchforks came out?

I'd start by testing the 4-pole isolator you used to isolate the power. Also check it's actually a 3pole and neutral isolator where the neutral is late break / early make, I've seen it where some nimrod has used 2x single pole isolaters/MCB's and fitted a rail between the individual levers to make it operate like an SP+N breaker so I wouldn't put it past someone to do something similar with a 4-pole MCB or isolator...

 

[DPG]

It's going to be a right kerfuffle with all the insurance claims. Especially when people claim for the brand new ipad which they had on charge at the time (honest guv)