3 phase problem after spark did 5 year safety inspection

[jimthegent]

Hi lads 5 year safety inspection the spark put the tails back and later line 2 of the 3 phase blew blowing the box off the wall and taking out the main fuse on the same line into the building can you all just say quickly what you think the spark may have done wrong ?
Cheers

 

[MJPD29]

There have been several reports of Hager RCCBs detonating when the test button is pushed which then blows the cutout fuse, it also happened to me a few years back, really loud.

Had it happen with a square d rcbo once. All further test buttons were pressed with eyes closed and touching cloth.

 

[jimthegent]

Had it happen with a square d rcbo once. All further test buttons were pressed with eyes closed and touching cloth.

Further to all that we had surge protection fitted but it still managed to turn pdu into molten plastic and circuit boards in scrap would surge protection be useless in this situation