Single core cable selection
Single core cable selection
(OP)
Hello,
I have 690V network, 3 phase system, no neutral, with 2400Amps load current.
I end up with 8 runs of 3 core 240mm2 cable size.
When I select 1 core cable, I can manage with 12 runs. It means only 4 runs per phase.
3 core cable in general has low current capacity than single core.
Is that possible? or am I doing something wrong?
regards
Avi.
I have 690V network, 3 phase system, no neutral, with 2400Amps load current.
I end up with 8 runs of 3 core 240mm2 cable size.
When I select 1 core cable, I can manage with 12 runs. It means only 4 runs per phase.
3 core cable in general has low current capacity than single core.
Is that possible? or am I doing something wrong?
regards
Avi.






RE: Single core cable selection
However, the method E is the method corresponding to F and the carrying capacity will be then 430A.
The air between cores facilitates cooling of cores by enhancing convection.
A conduit hinders heat evacuation by introducing a temperature drop in the chain of temperature drops.
RE: Single core cable selection
With single core it becomes easy for bending and termination. In the single core you don't need the break out space inside the cable box.
So if you want to increase the no. of cables, better not to do that and go for the single core 630mm2 conductor cable.
RE: Single core cable selection
RE: Single core cable selection
I was looking for an answer on, if I can use 12 runs of 1x120mm2 (4 runs per phase) instead of 8 runs of 3 core 240mm2.
regards
RE: Single core cable selection
120mm2 single core cable (Cu/XLPE) is not capable of carrying 600A per phase (2400A load/4). Did you mean 240mm2 single core?
Assuming you are using copper conductor XLPE insulated cable, then the "in Air" rating of a 240mm" is around 600A in Trefoil and in the horizontal plane, but that is without de-rating for grouping etc. If the trefoil groups of cables are spaced >2x cable O.D. then de-rating for grouping need not usually be applied, but you must factor in any other de-rating factors for high ambient temp. etc.
You don't say what the length of the circuit is, but at 2400A you will have to also give consideration to volt drop and earth loop impedance constraints.
RE: Single core cable selection
RE: Single core cable selection
Jghrist - You are correct, my bad.
I intended to say is 8 runs of 3 core 240mm2 cables as per calculation for 2400Amps, 3 phase current.
But when I select 1 core 120mm2 cable, then I see that 4 runs 1 core 120 per phase should be sufficient. So it makes 12 runs of 1 core 120mm2 cables.
The cables are laid in cable tray, open air. So my figures and sizes are based on the ambient derating + bunching factor in cable trays.
The cable manufacturer I used has
1 core 120mm2 cable with ampacity of 320 Amps
3 core 240mm2 cable with ampacity of 344 Amps
regards
RE: Single core cable selection
Suggest you get someone experienced in cable sizing to do the calculations for you.
RE: Single core cable selection
RE: Single core cable selection
Correct. When I do calculation its 2400 Amps. So considering balanced 3 phase, it is 800 Amps per phase.
So it means 4 runs of 120 mm2 should be good enough per phase (344 amps per run). Total 12 runs of 1 core 120 mm2 cables.
RE: Single core cable selection
RE: Single core cable selection
The problem is solved for me.
RE: Single core cable selection
Regards
Marmite
RE: Single core cable selection
I agree but per project requirements, It is not allowed to run more than 240mm2 cable.