Different voltage grade of cable on same cable tray

[shkim2000]

We have two different cable groups, 600/1000V(U0/U) for Low Voltage Power and control and 150/250V for instrumentation. Power is Ac690V and 400V AC. Some power control cables (for dry contacts) are driven by AC110V and DC24V employed as 150/250V cables. In the case that those power control cables(150/250V grade) are laid together with 690V power cables on the same cable tray, I do not see any problem but is was raised by someone as per spec. The mentioned problem is that earth fault power cable by damage causes insulation grade of control cable(150/250V).
I'm not sure if this is problem in technical point view or this is specification problem only.
Anybody helps my difficulties, please ?

 

[dpc]

It doesn't sound like you're in the US, but here in US, this is acceptable provided all of the insulation is rated for the highest voltage in the tray. If you have a 480V circuit in the tray, all cables must be insulated for at least 480V regardless of the actual voltage of the circuit.

 

[buzzp]

Thats interesting. I assume this is part of an NEC requirement. Do you know where off the top of your head this is talked about in the NEC? I have not been in this area long but was not aware of this requirement. Thanks.

 

[DanDel]

buzzp, it is in NEC Art.300.3(C)(1).

 

[shkim2000]

What about in Europe, in U.K.

 

[buzzp]

I see that requirement is for voltages of 600V or less. The OP has voltages above this so what would the requirements in the US be for the case of 690V circuit in the same raceway as control power (120VAC)? In reading the next section of the NEC (300.3(C)(2), it looks as though this would be allowed (thinking of motor power and control power here). Is this true? Thanks.

 

[dpc]

buzzp,

Above 600V, the basic rule is that the lower voltage circuits must be physically isolated from the the high voltage circuit by a metal barrier and **cannot** occupy the same raceway. Mixing would only be allowed for the narrow exceptions provided in 300.3(C)(2).

Your example of motor control conductors and motor power conductors would generally NOT be allowed in the same conduit if the motor feeder was above 600V. They can be in the same motor starter enclosure or within the same motor terminal box, but could not share a conduit or cable tray.

This rule is fairly sacrosanct in the US, at least in my experience. In fact many electricians insist that 480V and 120V circuit cannot be run in the same conduit, but this is incorrect as noted above.

 

[buzzp]

Ok, I understood that part correctly but failed to realize that circuits <600 had to have the same insulation rating if they are in the same raceway, conduit, etc.

Now maybe someone can answer the OP question concerning Europe.

 

[shkim2000]

Thanks
You all helps me a lot.

 

[shkim2000]

With regard to same insulated cables on the same cable tray, I needs to have any requirement in IEC/Europe. Anybody tells me.