Bang! - I knock out 1/3 of power in office wing!

[eveares]

About a month ago, I was in one of the office wings of the building that I work at.

Went out the fire exit to enter the internal fire-escape stairwell of the wing that I was in to grab some network cables that were in a box that I needed (box of cables was in stairwell).

On coming back into the wing with the network cables, I walked over a single silver metal floor socket where there was a distinct pop/bang sound what knocked out power to 1/3 of the wing and thus took out a bunch of peoples PC's. Only noticed the floor socket once I looked down after hearing the pop/bang sound.

No circuit breakers had tripped but instead It turned out that one of the main incomer fuses on one of the phases feeding the wing had blown!

Really not my fault in my opinion as walking over a unused silver metal floor socket should not cause what happened, but none the less was a unlucky event. Electrics and floor sockets are from the early 2000's.

Regards: Elliott.

 

[wwwebber]

How is this a DIY disaster ?

 

[geraldthehamster]

He did it himself..

 

[eveares]

He did it himself..

Exactly, in reality I think I must have disturbed a poor electrical joint in the floor when I walked over the socket.

 

[Michael Beaumont]

I was helping do some electrical testing in a warehouse when my supervisor at the time had managed to short a screwdriver in one of the main distribution boards which went with a right bang which blinded him temporarily. This had blown one of the main incomer fuses so YEB came with visor, leather apron and some kind of huge rubber space gloves to replace the 200 Amp fuse. In and out in an hour so the call centre ladies were soon back to work.

 

[opps]

some kind of huge rubber space gloves to replace the 200 Amp fuse

I did some work for a mate of mine a couple of years ago. He was too tight to pay his electricity provider to move the electricity supply from one side of the room to the other so he paid a guy who used to work for his electricity supplier until the firm sacked him for doing private cash in hand jobs.

He too wore rubber gauntlets as he stripped the insulation from the cables. I asked him how he knew when it was time to buy new gloves given that the armour braiding on the cable must take a heavy toll on the gloves. He said that as they reach the end of their working life you can feel a tingling sensation. I then asked him what would happen if the two phases ended up touching each other, would they blow the fuses in the green box out in the street and knock out the supply for the whole neighbourhood? He replied that it all depends how far away the box is, if it isn't very close all that would happen is that the phases would keep making very loud bang noises.

I decided to stay on the other side of the room until he had finished.

 

[John D v2.0]

No circuit breakers had tripped but instead It turned out that one of the main incomer fuses on one of the phases feeding the wing had blown!

Often where the transformer is big and close by, the let through is limited by the back up fuse, even if the rating is higher. This is because mcbs are mechanical but fuses just have to melt. In other situations both would go. The current would be many times the rating of both the fuse and the mcb, 10ka if you're unlucky.
This also saves you having to use huge cables where the fault current is theoretically high.