Exploding PowerPoint Mystery - Page 1
Forum section: electronics / general

author: Max1636
author_rank: Contributor
timestamp: May 29, 2023, 10:27:43 am
content: So I’ve got a bit of a strange issue that’s happened recently at my unit, I went to unplug a small Bunnings nightlight from a PowerPoint, I didn’t turn off the switch before I pulled it out but right as I did there was a bang and the active socket on the power point was black. The circuit tripped (RCBO) but it also tripped my Oven and Cooktop circuits (Both RCBO) but more worrying it also tripped the 50 Amp main switch (MCB) and it also tripped the 50 Amp main switch at the main distribution panel downstairs from my apartment.I’ll attach a photo of the power point, it looks like there was a big jump from active to earth? Funny thing is the Bunnings nightlight still works just fine, it also doesn’t even actually have an earth, just a note also all wiring in my apartment is brand new, all replaced about a year ago, everything on new Hager RCBO’s.I think I’ve had a similar event happen on 2 occasions in the past, where I’ve unplugged devices and for some reason right as I do this the RCBO trips, but I think the reason for the big flash was that my dryer was running, I think somehow having a big load on the circuit made the issue worse.Now to what I think is causing this but I’m interested to know what people think and why this could be happening, I think this is somehow being caused by my UPS, it’s an APC 3000VA unit, it’s not really old but could be as much as 8 years old. I think it’s the issue because it was previously on its own dedicated circuit but I temporarily had it on the same circuit where I plugged in the Bunnings night light, the 2 previous occasions where the RCBO tripped was when they were connected to the circuit with the UPS. I think the UPS is somehow back feeding power or something, I don’t see how else it could blow a 50 Amp breaker.Very curious to know if anyone knows how this could be happening? Of course I currently have the UPS disconnected.

author: NiHaoMike
author_rank: Super Contributor
timestamp: May 30, 2023, 01:22:58 am
content: Insufficient clearance between terminals, replace outlet with better quality one.

author: Max1636
author_rank: Contributor
timestamp: May 30, 2023, 01:46:45 am
content: Interesting thought but if you look at the photo I can’t see any way that the active could touch the (Correction - EARTH), it’s also not some cheap outlet is was a less than year old Clipsal GPO.

author: Nusa
author_rank: Super Contributor
timestamp: May 30, 2023, 05:39:38 am
content: Quote from: Max1636 on May 30, 2023, 01:46:45 amGround, not neutral. The prong on the nightlight has a burn too, right? Don't remove it from the mechanical equation.

author: Max1636
author_rank: Contributor
timestamp: May 30, 2023, 06:14:24 am
content: My bad I meant ground/earth I don’t know why I said neutral. Weirdly there is absolutely no burn mark on the light whatsoever, I’m looking at it now through a magnifier and there is nothing.

author: ejeffrey
author_rank: Super Contributor
timestamp: May 30, 2023, 11:38:10 pm
content: Possibly a scrap/filament of metal left from manufacturing that broke loose and bridged the gap then vaporized?

author: Psi
author_rank: Super Contributor
timestamp: May 31, 2023, 12:13:31 am
content: yeah, I'm thinking combination of very small clearance, and an arc forming as you pull out the plug due to some inductance.Normally that would be fine but if the plasma of that arc expands enough to touch the opposite terminal it will cause an immediate short circuit like this.But as said above, it could also be a metal shaving inside the socket that moved around until it caused a short.A lot of sockets are made in china with less than ideal safety standards.