paralell cable connection
paralell cable connection
(OP)
hi everybody!
I need your help for my issue, that is cable connection in paralell.
I have to supply for a load through an MCCB-3P-400V-500A. I used a Cu/XLPE/PVC/DSTA/PVC-3x240mm2-1x150mm2, but it was not cable to carry whole load. so I used one more Cu/XLPE/PVC/DSTA/PVC-3x70mm2-1x50mm2.
1. Is it ok to connect these two cables in paralell?
2. How can I connect 3 through-type Current Transformers in this case? Where CTs are connected before MCCB.
Thanks alot!
I need your help for my issue, that is cable connection in paralell.
I have to supply for a load through an MCCB-3P-400V-500A. I used a Cu/XLPE/PVC/DSTA/PVC-3x240mm2-1x150mm2, but it was not cable to carry whole load. so I used one more Cu/XLPE/PVC/DSTA/PVC-3x70mm2-1x50mm2.
1. Is it ok to connect these two cables in paralell?
2. How can I connect 3 through-type Current Transformers in this case? Where CTs are connected before MCCB.
Thanks alot!






RE: paralell cable connection
RE: paralell cable connection
If you are outside of North America, and not subject to stringent codes, you may parallel dissimilar cables. The cables will share the current in inverse proportion to the impedances of the cables. You should look up the impedances (NOT the resistances) and determine the percentage of the load that each cable will carry. Then check the cable ampacities to be sure that no cable is overloaded. Verify the currents with a meter after installation. It is still not a good idea.
Bill
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"Why not the best?"
Jimmy Carter
RE: paralell cable connection
You would need to pass both cables through the CT, if the hole is too small perhaps a short section of bus.
Warross,
Code issue aside would the impedance miss-match self correct as the overloaded cable heats up, raising the impedance. Does NEC even allow you to use conductors in parallel without special approval?
Regards
Roy
RE: paralell cable connection
RE: paralell cable connection
It has to be terminated the same, have the same length, same material, area, insulation and be 1/0 or larger. Each cable has to be sized handle the full load or each has to have its own protection
RE: paralell cable connection
I agree about same length, cross section, material, route, etc for paralleled conductors but this is a new one for me.
So in an installation with, say, 4x 500mm2 single core cables per phase where any one of those conductors is far too small on its own to carry the load current you say that each core needs its own protection? I am really surprised. I've never seen, or even heard of, an installation like that anywhere.
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If we learn from our mistakes I'm getting a great education!
RE: paralell cable connection
RE: paralell cable connection
Keith Cress
kcress - http://www.flaminsystems.com
RE: paralell cable connection
RE: paralell cable connection
RE: paralell cable connection
Keith Cress
kcress - http://www.flaminsystems.com