Single core or multi core power cable ?
Single core or multi core power cable ?
(OP)
What is the difference between single core and multi core power cable? I mean when we deciding to use single core and multi core power cable? For example 3x1x240sqmm for 3,3 KV or 1x3x240sqmm for 3,3KV






RE: Single core or multi core power cable ?
G.F.
www.engineering-services.gr
RE: Single core or multi core power cable ?
G.F.
www.engineering-services.gr
RE: Single core or multi core power cable ?
1)A typical 6kv N2XSY 1x240 cable has aprox. 3kg/m and maximum bedding radius of 15x40mm=0,6m while,
2)A typical 6kv N2XSEY 3x240 cable has aprox. 11,5kg/m and maximum bedding radius of 15x75mm=1,12m.
So taking in mind your cable data and depending on the cable routing you can decide what is the best from cost point of view.
Please note that in general one three core cable is cheaper than three single cores.
G.F.
www.engineering-services.gr
RE: Single core or multi core power cable ?
If the cables run in the same conduit no difference will be.
RE: Single core or multi core power cable ?
Bill
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"Why not the best?"
Jimmy Carter
RE: Single core or multi core power cable ?
If the cable routing includes underground duct banks and/or conduits, a three core cable with earth wire is too large to fit in commonly available conduits or to be able to negotiate a conduit bend during pulling. Three core cable costs more than single conductors for the cable but single core usually takes more manhours to install since there are three or four reels to position for each pull.
Installation costs are proportional to weight of installed cable and devices. Single core reels are lighter and easier to handle. Pulling and handling three lighter single conductors may be less expensive than one heavy 3/c. (Our historical installation costs are not granular enough to determine the better method).
The counter argument is that the three core cable is difficult to handle in the cable tray or vault and the connection fitting costs are expensive. (No special cable glands for single core). If the project is in a high cost labor area, we may use more multi-core.
But in Africa, our affiliated company's project used all 3 and 4 core cables for 600V, 6.6 kV and 11 kV, including a lot of 1200 mm2, 3/c with armor. Labor was inexpensive and cable routing was designed to accommodate the wide bends.
In North America, there is a perception that all cables must be enclosed or protected in a conduit. Open wiring, as is common in the rest of the world, is frowned on by owners, inspectors and especially the electricians who are very good at bending and installing steel conduit. That requirement makes single core the design choice even though a multi-core routed in cable tray would be just as rugged and reliable.
RE: Single core or multi core power cable ?
RE: Single core or multi core power cable ?
RE: Single core or multi core power cable ?
RE: Single core or multi core power cable ?
I am referring to the phase geometry inter-set not intra-set.
When you parallel 2 cable sets in trefoil (?triplex) they should be arranged as:
A A
B C C B
Much easier to guarantee this formation if they are multicore instead of single core.
RE: Single core or multi core power cable ?
Much easier to guarantee this formation if they are single core instead of multicore.
RE: Single core or multi core power cable ?
That's interesting. I've been doing this a long time and never heard that argument before.
There should be very little flux outside the triplex cable, so why would the interposed phases between the two cables really matter much.
In the 480 V commercial world, it is common to see feeders consisting of up to 10 conductors per phase pulled into 10 conduits using triplex or three single conductors pulled in at random. This is allowed under the NEC and I'm not aware of any serious issues that have occurred.
RE: Single core or multi core power cable ?
In this case a very small amount of the magnetic flux will flow outside. So you don't need to carry of parallel cables current unbalance.
Straight laid single-core cables even pulled close each other a current unbalance could take place if they are not in a certain order.
A good indication how to lay the phases is in the Prysmian
http:
The text is in Spanish, indeed, but the sketch is very clear.
Second, the cable reactance will increase with the cores centerline distance. On the other hand the temperature will decrease with
the distance between cores[ and cables, of course]
RE: Single core or multi core power cable ?
You're right, multicore cables twist the phases together - so no issue there.
dpc:
I would have thought paralleling single core cables with random arrangement as you described would cause some rather nasty current imbalances?
RE: Single core or multi core power cable ?