Sort This One Out

[RussellR]

Anywhere near high voltage ?

 

[seajayess]

No just low voltage CJS

 

[Apache]

No you dont seem to understand there wasn't 238 volts to earth from the SWA there was 238 volts between the SWA and the live line conductors, but the SWA wasn't connected to anything just like a piece of cable lying through the building CJS

Hang on here CJS. I don't mean to be rude but your explanation isn't quite clear.

ARE you saying you put one probe of the volt tester on a live terminal somewhere on the installation and the other probe onto the SWA armour?

If yes you would expect the mass of the SWA to act as a crude but poor earth rod and give you the potential difference you describe. No?

Did you measure amps?

We NEED to know exactly what your ends of the voltage tester were touching!

 

[dixon9]

A possibly stupid question BUT...

Did you do the same test with a different meter?

 

[dixon9]

...and another one:

Is there any type of capacitor(s) inside the control panel?

 

[spinlondon]

Could it be possible, that the cable is acting as a capacitor.

Perhpas you could ground the cable ends and the SWA, then test for voltage.

 

[elvis]

How is the cable fixed? Is it banked with other cables?

I know you said you inspected the length of it but you are getting 240V, stinks of screw through 2 cables to me.

 

[The Godfather]

Could it be possible, that the cable is acting as a capacitor.Perhpas you could ground the cable ends and the SWA, then test for voltage.

I'd be rather wary of doing that, until the source of the 238V is established.

Don

 

[elvis]

I know it's a factory but I'd have a tester across the supply on the cable and flick off each of the circuits on the board individually (where possible) to see if you can isolate where the voltage is coming from.

 

[binky]

Have had induced voltage causing LEDs to glow dimly before, but never with such a high voltage showing. Think elvis has the right idea.

 

[The Godfather]

I know it's a factory but I'd have a tester across the supply on the cable and flick off each of the circuits on the board individually (where possible) to see if you can isolate where the voltage is coming from.

Excellent.

(Assuming, the site can be isolated without loss of production?)

The Godfather

 

[seajayess]

Ok people you all seem to be thinking in the wrong direction. There isn't an induced voltage of 238 volts, if anything it is at 0 volts. The cable is removed from everything so just like a piece of SWA lying through the building and def not touching anything, and the cable is def not damaged in any way.

The voltage we are getting is from a live source to the SWA internal conductors, which is NOT connected to anything even the steel wire armouring. So why are we getting the potential difference of 238 volts CJS

 

[batty]

Has to be induced voltage try connecting armour to a reliable earth and test again.

Batty

 

[elvis]

Check yer tester then phone Mulder and Scully ?:|

 

[RussellR]

Is the air damp ?

 

[seajayess]

Its a steel clad building and the internal factory is made from freezer panels and the SWA is in the roof space CJS

 

[Apache]

Ok people you all seem to be thinking in the wrong direction. There isn't an induced voltage of 238 volts, if anything it is at 0 volts. The cable is removed from everything so just like a piece of SWA lying through the building and def not touching anything, and the cable is def not damaged in any way.The voltage we are getting is from a live source to the SWA internal conductors, which is NOT connected to anything even the steel wire armouring. So why are we getting the potential difference of 238 volts CJS

Not ALL thinking in the wrong direction.........

ARE you saying you put one probe of the volt tester on a live terminal somewhere on the installation and the other probe onto the SWA armour?If yes you would expect the mass of the SWA to act as a crude but poor earth rod and give you the potential difference you describe. No?

:|

 

[RussellR]

Are you saying it is effectively earthing through the air Apache ? I have seen when fault finding panels floating voltages, when circuits are not pulled down to earth.

A similiar effect ?

 

[Apache]

Are you saying it is effectively earthing through the air Apache ? I have seen when fault finding panels floating voltages, when circuits are not pulled down to earth.A similiar effect ?

of just the general mass of the SWA?

There will be a decent mass of steel, CJS doesn't say what size or how long, but we would have a good few kilo's of mass that would only need to take a few miliamps to give a voltage reading.

 

[SPECIAL LOCATION]

Ok people you all seem to be thinking in the wrong direction. There isn't an induced voltage of 238 volts, if anything it is at 0 volts. The cable is removed from everything so just like a piece of SWA lying through the building and def not touching anything, and the cable is def not damaged in any way.The voltage we are getting is from a live source to the SWA internal conductors, which is NOT connected to anything even the steel wire armouring. So why are we getting the potential difference of 238 volts CJS

Right... Let me see if I can get me head round what you are saying here.

Q1/

I couldn't see any reference as to how long this run of SWA is?

I assume its long!

Q2/

I couldn't see any detail about the "type" of meter you are using?

I assume a typical high impedance multimeter,

(e.g. one which would put approx 10megohm - 15megohm across the voltage probes, when taking volt readings)?

Q3/

I assume your reading is 238v 'AC' NOT 'DC'?

Q4/

Are you saying you have one meter probe on any one of the cores of the SWA

and the other probe on a "LIVE" (230v) conductor somewhere on a local supply?

OR is the second probe on a 'Neutral' or 'Earth' conductor?

I read it that you are across 'Live' (230v) & a core of the 'open circuit/disconnected' SWA ?

IF all of my assumptions are correct....

Then your 'apparent' 238v reading probably sounds right to me? :|

e.g.

You have one ruddy great big aerial cable lying across some part of the factory.

You are measuring the centre core of your aerial against a reference point that is fluctuating between, 0v, +230v, 0v, -230v, 0v, +230v, 0v, -230v etc.. etc...

Whatever potential your aerial is at..

it is being measured against a varying reference point ..

thus an apparent 230v signal.

Go try it at home on your analogue TV aerial...

Disconnect all you TV gear.

Put one meter probe on the centre pin of the "open circuit" aerial down feed termination.

Put other meter probe on a 230v live supply from a nearby socket outlet.

you will get an apparent 230+v between a "live source" and your Open circuit cable.. just lying there connected to nothing.

Thats all I can think of from info given? :|

Now...

If I have my pants on backwards and you are referencing your SWA against Earth or Neutral... you wont get the 230+v

Then I would need to go back in me box and think again... :_|

probably need a bit more info though!? ? :|

:coat