Cable voltage ratings

[jnb]

If I twist together two 300V rated pieces of cable does that mean they are rated to withstand 600V of differential voltage? and what can I rely on them to handle in the real world?

[Speedskater]

Yes, wire to wire 600V is OK.
How much can they handle? Well above about 1000 Volts things start to get strange. But one day at work I test some multi-conductor 22 or 24 gauge wire (sort of like CAT-5) it made it to almost 2000 Volts!

[kevinkr]

For safety reasons I would not exceed the 300V rating to the outside world, conductor to conductor is a different matter as long as no conductor exceeds 300V relative to ground. Actual insulation breakdown will generally occur at much higher voltages, but with AC at least leakage currents to surrounding objects might be a problem.

When you say cable, do you mean cable or wire? (Cables are generally understood to be multi-conductor while wire is single conductor.)

For individual wires you can always augment the existing insulation by slipping the wire into some pvc or similar tubing, this unfortunately doesn't work for cable.

[jnb]

Thanks for the replies. Just to clarify I did mean wire. I am interested in wire to handle mains (339Vp) and a 550V supply. I have done some construction already, and I can see where I should go back and sleeve some of it.

[MRupp]

There was an interesting article on tube amp cabling in a recent German elektor issue, written by a respected designer. He recommends to always use double insulation or extra sleeving on all mains carrying cables/wires. And as far as the 550 V HT supply, I think it would be safer to use a wire which has at the very least a 550 (600?) Volt rating.