Utility Cables - Why 600v/1100v Cables are Used for 415v System?

The 600/1100 is the insulation voltage rating of the cable. It has nothing to do with the system on which they are used. In the US, the 600v cable is used with 120v, 240v 208v and 480 v systems.

The insulation may also need to be rated for peak voltage rather than RMS. [?]

Quote brzk "1_600 volts is for Neutral or Earthing wires, 1000 volts for Phase wires (or said conductors)."

Not in the US. As I said, 600 v conductors are used for 120v, 208v, 240v, and 480v systems. Earthing, grounding or bonding conductors can be insulated or bare. Grounded neutral conductors are insulated with 600 v insulation.

Hello WarEagle,

OK, noted. General European rules are quite different.

Except to put metal of swgr to earth and for earthing of outward installations, bare conductors are forbidden ( exception: power copper or aluminium busbars) because of pregnant lighning protection. Thank you for your kind answer, BRZK

They were not talking about US. They were talking about Europe. No-one cares about US voltages. Question asked for BS/IEC, not NEMA/IEEE

You are refering to BS7671.

The UK also uses 550V and 660V for industrial, so where do we set the standard?

I was brought up with 550V as the standard voltage on all our plants.

BS 7671 gives current ratings of LV cables with pvc/xlpe insulation,copper/aluminium conductors,armoured/non-armoured finish made to BS6004,6231,6346,7629,5467,7211, 6724,6007,6883,6207,6500 but voltage ratings are not given. Cable manufacturers indicate voltage ratings in their price list and literature. In some tender documents 300/500V too was mentioned. I wonder why BS7671 or On site guide didn't advise appropriate voltage rating for selecting cable for 230V single phase and 400V 3phase use. As Megger tests are done at twice rated voltage 400V cable should withstand nearly 1000V.

Thanks for your thoughts, my main issue was recognising that the rated voltage is actually the insulation rating and calculated using the peak not RMS value. Thanks also for the ref to the BS7671! :) Hope this thread helps others too!

I'm no Electrical engineer but I would think that if you used a 415v cable supply, by the time the power gets where it's needed the drop in voltage will affect the plant or whatever you're running, it's better to over supply & transform down to what you need, also you can supply more than one location with the one supply. If anyone disputes this please refer to the first few words of this reply.

Bazzer.

660/1100V refers to phase to earth (660V) and phase to phase (1100V).

So given a fault situation phase to phase voltage could appear as phase to earth. It would be an unusual fault on a star / neutral grounded system, but quite feasible with a delta system.

Think about it.... When you perform your insulation test, What voltage do you set the meter for???

For 240V circuits, we test at 500V.

For 415V Circuits, We test at 1000V.

The insulation has to be rated to twice the voltage of the circuit.

This also identifies whether the cable you have at hand is suitable for LV, HV or not at all!

Regards,
Sapper

Presumably because if they were, and the transmitted voltage were to rise by say 10%, then they would be under-rated.