Busway for factory

[honglien]

Hello!
I have just jointed a Electrical Designing Department and we have a project. We supply an industrial factory, that is a cement factory. On the MV side of the factory net, we connect to Local Network (24kV) of the Power company using single core cable 24kV-Cu/XLPE/PVC/DSTA/PVC-1x240mm2, which 3 wires for a phase, so the amount of cable too much, which the total is 9 wires , in my opinion. I want to use multi-core cable 24kV-Cu/XLPE/PVC/DSTA/PVC-3x240mm2, which the total is 3 wires. Could you suggest me either to use 9 wires single core cable or 3 wires multi-core cable?
Thank you in advance!

 

[davidbeach]

If I read that right you are asking if your should use 9 conductors or 9 conductors? If that is correct, there is probably no right answer but the best solution will depend on various local factors.

 

[waross]

The impedance will probably be different with single conductors versus 3x cables.
The impedance (Mainly reactance) is often unsymetrical in a single cable installation. This may or may not be an issue. Transitions may or may not be used to balance the impedances.
The impedances in a 3 conductor cable are balanced.
Induced voltages in the sheath may be an issue with single conductors but will be negligible with 3 conductor cables.
Spaced single conductor cables often will have a higher current rating than 3 conductor cables of the same size.
An insulation failure will take out one single conductor versus 3 conductors in the multi conductor cable.
The labour to install duct banks and cables may be less with 3 conductor cables.
Three conductor cables take less space for installation.
Most of these issues vary from one installation to the next. For instance, the impedance issues may be serious in one case and negligible in the next case.
both systems are widely used.
Davidbeach summed it up well:

If that is correct, there is probably no right answer but the best solution will depend on various local factors.

respectfully

 

[honglien]

Thank you, waross and davidbeach. I am not native English speaker, and my English is not very good so I didn't descride the issue clearly. You give me very useful answers. Thank you!