So on Sunday I was called out to a house in my village where the owner was having problems with his electricity - said he has getting static charges from stuff.
A TN-S supply similar to this one
A call to Northern Power got an engineer out within the hour and 3 hours later the road was closed and dug up.
Without the mains bonding I am sure it would not just have been a tingle he felt.
So had there been a live to Earth short then? Wouldn't that trip a protective device upstream?
Or was it a case of earth becoming detached at the substation end and mutual inductance between the live and earth?
I'm trying to work out what a L-E fault means. If E is tied to N somewhere (at the substation in a TN-S system), then it's effectively a L to N short. Won't that result in something getting very hot, if not blowing some fuses?
Or it was a high resistance L to E connection, in which case it may be a fair fight between the resistance of the short and the resistance of the earth bonding?
Theo
It was the latter here when the metal switch faceplates around the house were tingling. I measured the local earth impedance as being a bit over
100 ohms. Opened up the main consumer breaker and found the imbalance detector had been isolated.The work of a professional, no doubt. I reconnected the detector and checked its trip current. Also addressed the actual L-E leak.
At that time PME was added to the street supply. Impedance was 1/3 of an ohm. Would it be worth having the house PME'd or better to let sleeping dogs lie?
PA
PA
I recently had a case like this where the neutral point (and earth) was o/c in the road. When you put the kettle on the lights seriously dimmed! And I guess the neighbours got more than 240V!
Thankfully no equipment was destroyed and the matter sorted over a period of 24 hours and included digging up the road. In the good ole days I would expect some incandescent bulbs might have popped!
Well you say that, but a lot comes down to skin resistance. My skin is rather dry and gnarley which gives it a high resistance. So I've got into the lazy and deprecatable habit of testing if something's live by sticking my fingers in the socket (don't try that at home, folks). I just feel a tingle which slowly builds up over several seconds. Mind you, if my hands were moist, I could be in a lot of trouble. Can't afford complacency with slapdash habits like that.
I was pretty sure that L and N were fine and the sheathing on the incomer cable had gone live.
So if only the cable sheathing coming into the house had gone live and was not earthed back to the substation then nothing would have tripped.
Removing the main fuse left the incomer sheath at 251V.
Did you check any of the neighbours to see if they had the same fault ?.
Yes I did. That was one of the first things I wanted to check.
I managed to check two out of the three closest neighbours houses. They were OK.
Every other house usually as they will be on the same phase. Brian
This reminded me of the old cable that was feeding a garage back in the50s when my family moved in. The lights and three core plug worked of course, but one day when a heater was on in the garage as I walked up the garden, I could hear this sizzling noise. On close inspection there was a smell of rubber on the fence. The cable was of the older rubber covered kind, three core but the earth was bare wire. Turning it off at the house and inspecting with a torch showed little tooth marks at the points where it was sizzling. As we never actually found any electrocuted mice or rats, then I must assume that they learned their lesson. Its now an armoured cable that goes down the garden!
Brian
every 3rd surely ?, but they are ?all on the same company-provided earth arrangement, which was the problem.
Andrew
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