Armour sheath carrying a voltage

[sdc8843]

Hi guys,

Had a situation the other day where the armour sheath on sub mains was carrying a voltage of about 55V.The sheath was not being used as an earth and was only there to give protection to the cable. Can anyone tell me why this occured?

Many thaks

 

[Deleted member 9648]

Was the armour properly bonded to a reliable earthing system?....probably not I'd wager.

 

[Marvo]

If you were using a digital tester, their high input resistance makes then very sensitive to voltages induced by capacitance. Try the same test with an analogue instrument and you'll probably get a very different result. It would be good practice to earth bond the outer armor of the cable using an SWA gland and earth ring or copper strapping.

 

[sdc8843]

Sorry should have said, the armour hadn't been earthed to the trunking. But what i would like to know is why the sheath was carrying a voltage.

 

[Sintra]

As Marvo has said it is most likely an induced voltage.

How many cores are in the SWA and why is the armour not connected to earth?