Voltage between hot & insulation of XLPE cable

Haven't seen build up, but did experience some interesting surprises while doing work experience in coal mines on trailing and equipment cables. (Spent 2 weeks int he cable repair shop.)

Is the voltage really "building"?

What I saw (or as it was explained to me) was that whenever a cable is disconnected, the cable can act as a capacitor and maintain the line voltage that was present at the instant it was isolated from the circuit. This is even true when the line is isolated by switch before removal from the coupling. In multi phase cables, at least one conductor will have significant potential relative to anything else.

I was taught a standard practice to discharge all conductors on a cable before doing any work with them.

The other observation was that the cables themselves could (again capacitive effect) be grounded at one point then transported to another where they showed a differnt potential relative to the equipment and other ground in that zone. (This voltage however was substanitally less.)

We had 1100 Volt cables that could store enough charge to vaporise 2mm off the end of a 2mm wire during earthing, so the energy available was significant and could easily be interpreted as voltage build up.

If you do have voltage build up, can I have the cable? I think you might have discovered the source of free energy that everyone is looking for.

Hi hara143,

Question before trying to answer ...

How did you measure the voltage difference?

Wangito.

This sounds like a problem called "Skin Effect" and it ressults from the current travelling on the surface of a conductor due to lower resistance. I would check all terminations and joints and then re-do the stress-cones.