Discuss Suspected Broken PEN conductor on TNC-S system in the ElectriciansForums.net News and Updates area at ElectriciansForums.net

sm_keeley

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Hello everyone,
I’m based in the ROI and live in a rural location. Yesterday evening my electricity supply started to switch on and off randomly. After waiting for the evening for it to come back on it still has not. I checked my neighbors who are on the same DSO as my house and they all have power.
I checked electrical items in my property, I have a metalworker single phase which has blown out two of its 2amp fuses. Everything else seemed to be ok. To be safe I isolated the mains switch and called my electricity company. They said check all your RCDS/MCBS ect which I’d already done. They’ll send someone out as soon as possible.
I decided to check the voltage across live and neutral conductors with my multimeter 10volts before the isolation switch. I then used a electric tester screwdriver to see if it lights up, to my suprise live, neutral and earth all show voltage.
My initial logic would suggest the possibility of a short circuit within the concentric main cable running to my home? I mean the live phase conductor has got hot, melted the insulation around it and then caused a short circuit to the neutral. This in turn then sends a current through the earth that’s why all three conductors L,N and E show current?
I called my friend, he’s a trainee electrician he suggested it could be a Broken PEN conductor. He came by, confirming I had a TNC-S system, he disconnected the mains so that the Live and Neutral are floating, these both still showed current when touched with a electric tester (lights up neon bulb on both conductors) but earth in my home consumer unit now doesn’t read current.
We went over to the DSO Pole that supplies my property, my friend said we should be careful as current could be present via the ground.
We checked the PME earth that connects to the main neutral supply into my property and this had current. (Mains supply still floating in my property) my friend thinks it’s a broken PEN in other words the neutral on my supply pole has burnt out and current is finding it’s fastest way to earth. Or could it be a short circuit in the concentric mains wire to my property? But if it was a short circuit wouldn’t there be arcing noises? Smoke and possibly fire? Or does the PME earth stop this and act as a path to neutral? I always thought power needed to return to source so ruled that out? Anyway, I appreciate any thoughts!
Rather interesting!
 

davesparks

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Don't trust anything a neon tester or non-contact tester appears to show, your trainee electrician friend will have already told you this I am sure.

I think it will be impossible to diagnose this remotely without some actual voltage readings taken with a suitable voltage tester.

It may not be what you want to hear but I think you will just have to await the arrival of a technician from your electricity supplier.
 

Risteard

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As above. Also PME doesn't exist outside the UK. Almost all installations within the State are TN-C-S - TT has pretty much been eradicated. Incidentally, everyone has the same DSO as ESB Networks is the only DSO within the State.
 

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