Oh dear!

[Deleted member 174758]

Just a little bit of news from sunny Swindon. But for those with less time, here's the crux of the story:

I just have to wonder why the guy was drilling in the garden. In any case, if the mains hadn't got him the induction heater? (coiled cable) behind him might have done instead, eventually. Brave try for a Darwin Award, but no banana this time

 

[Notch7]

Im surprised a drill with a plastic body would transmit enough to cause such injuries.

 

[Harry Bloomfield]

if the mains hadn't got him the induction heater (coiled cable) behind him might have done instead, eventually.

A common misconception. The heat has nowt to do with induction, more to do with the resistance of the cable producing heat and the heat not being able to escape due to the cable being tightly coiled, with no cooling air flow. Intermittent operation of a drill, is unlikely to be an issue. Long term continuous running of things like a heater, running close to the cables maximum rating, are more of an issue.

 

[Mottie]

I see what they did there.

"The incident sparked a localised electricity outage, which was later restored by West and West Utilities".

 

[Munroast]

How deep has he being drilling or how shallow was the underground cable. Also curious as why he would be drilling into the earth?

The main culprit here has to be how shallow a buried mains cable is. At this moment the bloke has my sympathies.


I also can't see any prob with them few coils still around the drum, esp for what a little drill would draw

 

[bernardgreen]

The drill appears to have suffered blast damage from an "explosion" that occurred as the conductors in the cut cable were shorted together ny the drill bit.

This explosion or more accurately sustained arcing would have continued to burn until the breaker at the substation operated.

 

[Notch7]

How deep has he being drilling or how shallow was the underground cable. Also curious as why he would be drilling into the earth?

The main culprit here has to be how shallow a buried mains cable is. At this moment the bloke has my sympathies.


I also can't see any prob with them few coils still around the drum, esp for what a little drill would draw

My guess would be to bang in a post of sorts.

 

[Deleted member 174758]

A common misconception. The heat has nowt to do with induction, more to do with the resistance of the cable producing heat and the heat not being able to escape due to the cable being tightly coiled, with no cooling air flow. Intermittent operation of a drill, is unlikely to be an issue. Long term continuous running of things like a heater, running close to the cables maximum rating, are more of an issue.

Point taken, Harry - I'm a better chippy than I am a sparky, although I have seen the big, scorched rubber balls that result from a wound-in cable being left plugged in over a bank holiday weekend on a couple of occasions (and been told that it was at the point of combusting)

 

[Deleted member 174758]

How deep has he being drilling or how shallow was the underground cable. Also curious as why he would be drilling into the earth?

Me too

Only time I ever did something like this was when I went through a heavy mains cable buried inside a stud wall which I had been reliably informed was isolated, Big blue flash and a bang, bit a large chuck out of the blade and I got thrown off the ladder and across the room (muscle reaction?). I got off light, I reckon

 

[Harry Bloomfield]

Point taken, Harry - I'm a better chippy than I am a sparky, although I have seen the big, scorched rubber balls that result from a wound-in cable being left plugged in over a bank holiday weekend on a couple of occasions (and been told that it was at the point of combusting)

As said, it a commonly misunderstood phenomenon, even amongst electricians who really ought to know better. While ever the flow and return wires (L&N) follow the same route, as they would in a flex - the two cancel the induction of each other out.

Something I often see on touring caravan sites and it makes me wince, is the orange hook up lead neatly rolled up on a drum. The plastic drums are usually sold separately to the cable. The end result of surplus cable neatly rolled looks neat and tidy and no problem if the cable is only providing for a few lights in summer, but in cooler weather it could be supplying power for heating and hot water. I will not use a drum for my cable, it is just formed into a figure of 8 and dropped in a supermarket bag.

Some commercial extension reels include a thermal trip cut-out, to avoid over the heating.

 

[Larry1990]

I installed some ground screws recently and the instructions were to drill a pilot hole in the earth with a 450mm SDS drill bit. Not sure if a mains cable would would be at that level?

 

[Deleted member 174758]

I believe this is current. Certainly seems to conform to the depths we were given when I was on a course 3 years back:

Of course, that's no guarantee... Which is why anyone working for a utility company uses an underground cable detector or even GPR (ground penetrating radar) on some jobs

 

[Larry1990]

No skimping on the digging when i get to the services trench...

 

[Munroast]

Why would he get a shock,

I believe this is current. Certainly seems to conform to the depths we were given when I was on a course 3 years back:

View attachment 271435

Of course, that's no guarantee... Which is why anyone working for a utility company uses an underground cable detector or even GPR (ground penetrating radar) on some jobs

what classifies as Low Voltage here?

I always thought it was 600 for everything - I have put a lot of fence posts in in my time, always thought 2 foot down was safe, never come across electrics but seen plenty pipes. even burst a few open.

 

[Deleted member 174758]

Regardless of what people are  supposed to do, they don't always do it, especially on older houses. I've lifted flags in a back yard to find water pipes just beneath them. Same story with those pocket sized front gardens some Victorian houses have - my own experience is that the mains under them is often nowhere near deep enough. And you can forget concrete over the top or even the yellow plastic warning tape