Outside with my electric hedge trimmer thingy I didn't get much done because there was a visible flash and a quiet 'pop' as I cut through the power cable.
I repaired it with a cable connector fitting, and was suprised to find no fuse blown, nothing tripped. Is that normal? or desirable?
TW
Normal half the time.
Is the circuit on a RCD? If not then fitting one e.g. at the socket you're likely to feed garden tools from is a good idea.
Often totally normal. The cable will be long and thin limiting the fault current. The trimmer will cut through the cable very quickly. It's probably double insulated without an earth core so there will be no earth fault.
I have cut through cables on trimmers many times and never tripped or blown anything.
Philip
I don't see how cutting through a L+N cable with double insulated hedge trimmers is going to trip any RCD.
There should be no passage of current to earth, assuming the cable landed somewhere dryish.
Depends if the business-end is in contact with the greenery at the time?
If it only nicks the insulation, it could prevent a shock for anyone touching it afterwards
Often it's tripping that leads to cutting the cable.
Bill
Fairly normal. My neighbour did the same yesterday, and I repaired the trimmers for him, but by disassembling them, the one tense moment being when they fell off the table and one of the brushes popped out and became a pingfuckit. It didn't trip any breakers/RCDs.
Normal; yup, not uncommon. Desirable, not really - but not always easy to do much about it. The usual problem with long leads like that is their loop impedance can be relatively high - so the fault currents you see are not huge. High enough for a flash and a pop, but not enough to instantly blow the fuse or trip a circuit breaker.
The advantage of the RCD is not that it necessarily will trip when cut, but it will protect the operator after when there is a risk of contact with an exposed conductor.
Done the same with the lawn mower. Didn't blow fuse, RCD or MCB. The short circuit was probably far too short.
...
One of the weakness is that although braid coverage is specified (>50% ) neither a braid strand size nor a braid resistance per meter is guaranteed...
and under certain conditions the armour resistance in the middle of a long run can be too high to meet instant MCB tripping for a nail penetration type accident, even if both ends are strapped to a copper core.
Owain
Try it next time whilst standing barefooted in a paddle.
*puddle*
Neighbour cut her hedge trimmer cable and it tripped the plug-in wylex MCB that had replaced the original rewireable fuse holder. 30 Amp one too.
I did that twice many years ago. I was using an attachment on an old Black and Decker metal bodies drill. First time no problem, drill just stopped. Second time cable snagged on the cutter leaving me with a dose of St Vituas's dance.
It takes a finite time for any short to trip a fuse or breaker. Your short may have been too short. ;-)
I cut my ring final cable* and it didn't blow the 30A rewireable fuse. I don't know what current was flowing but it took out my cable cutter blade and made lots of pretty sparks until I carefully opened the cutters and removed them.
Owain
With a modern plastic bodied double insulated tool, you are unlikely to see any difference in outcome.
The problems normally start when someone picks up the cut end for a closer look!
I am not sure how to take that, but I think I will go with 'jocular banter' and laugh and move on. TW
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