230v between live and earth on the incoming supply cable insulation

[millar]

NEUTRAL EARTH FAULT
I would just like to correct my message title for me mucking up :13:

A guy I work with was sent to change a mains board the other week. He isolated the supply and proved it was dead, He started stripping the board out and got a zap! He checking and noticed he got 230v between neutral and earth on the cable insulation ! This is what he had touched.
Has anyone every come across this ? The supply was old, im not sure what kind but I think he said it was a rubber cable. An older spark told us they used to make the insulation with some conductive compound materials incorporated into the insulation years ago ?

 

[daniel hill]

Am i wrong, you are saying 230v between live and earth ?
i have got that for the last 10 years ?

 

[Engineer54]

An older spark told us they used to make the insulation with some conductive compound materials years ago ?

Please!!...... how the hell can you have a conductive insulation?? Were not talking talking about MV cable here, that does have a semi-conductive layer over the conductor insulation!! ...Were talking about 600/1000V standard insulation grade cables.


Obviously he hadn't isolated correctly, or... the means of isolation wasn't isolating correctly!!!

 

[simpson93]

got there just before me, you just havent isolated properly- also havent tested properly to prove isolated.

 

[millar]

Im just re- telling what he told me, this was a domestic installation and the insulation of the cable on the scottish power side was live! The only thing we could think of was a break down in the insulation of the cable and they were pressing on each other at some point.

His hand only touched the insulation of the cable. not copper

 

[benji]

not a concentric cable is it

 

[Rockingit]

Did he tell this story after he'd found the bubble for his spirit level?

 

[millar]

haha he had a long stand first

Iv just txt him to find out what the outcome was,

As I say he isolated the mains board and removed the tails and put the cover back on the isolator switch. The shock was from the supply cable before the fuse I still dont understand it to be honest.

I await his response

 

[millar]

sorrt guys Major typo error Should read neutral to earth

 

[GaryM]

Well technically you were correct anyway as neutral is indeed a live conductor!

 

[Engineer54]

As to the conditions you have stated, this is just a fairy story/tale covering up his own failings somewhere along the line.

 

[millar]

Il stick with my muck up on the story.... no excuses for that one haha

Our gaffer went out and also tested it and got the same result. Scottish power came out to deal with it.

 

[Deleted member 26818]

Sounds like a lead sheathed cable to me.

 

[i=p/u]

scooby doo, is great at solving mysteries, i would say maybe insulation breakdown, or maybe incorrect polarity aswell...