Paralleling Different Cable size
Paralleling Different Cable size
(OP)
Hi,
What will happen if 4/O and 240mm2 underground medium voltage 33kV cable is paralled? it's used as a part of overhead line 33kV at the beginning of the circuit.
Regards,
Eskim
What will happen if 4/O and 240mm2 underground medium voltage 33kV cable is paralled? it's used as a part of overhead line 33kV at the beginning of the circuit.
Regards,
Eskim





RE: Paralleling Different Cable size
You'll need to be a little more specific about what you're after...
Dan - Owner

http://www.Hi-TecDesigns.com
RE: Paralleling Different Cable size
I believe that it is a violation of North American codes to parallel dissimilar conductors.
Bill
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"Why not the best?"
Jimmy Carter
RE: Paralleling Different Cable size
RE: Paralleling Different Cable size
Just for fun, here is an attempt to think through the physics fwiw:
IF we have two very small conductors of different size, the impedance is dominated by resistance which is inversely proportional to cross sectional area. The current in parallel conductors would be inversely proportional to resistance and therefore directly proportional to cross sectional area. In other words amps/mm^2 would be the same in each conductor and heat generated per volume would be (approximately*) the same in each conductor. The smaller conductor has more heat-dissipation surface area per cross-sectional area, and therefore would run cooler (assuming the same insulation thicknesses and ambient conditions etc).
IF we two very large conductors of different size, the impedance is dominated by inductance, which is roughly constant. So both conductors would carry roughtly the same constant. The smaller of the two conductors will generate more I^2*R and tend to run at higher temperature.
So the result is different depending on whether we're comparing too large conductors or two small conductors. (for small conductors, the larger of the two runs hotter, for large conductors the smaller of the two runs hotter).
* In both cases the temperature coefficient of resistance effects would cause more current in the cooler conductor and tend to bring the temperatures slightly closer together.
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(2B)+(2B)' ?
RE: Paralleling Different Cable size
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(2B)+(2B)' ?
RE: Paralleling Different Cable size
Which one is correct for the following:
- Phase A =OK to have two different sizes conductors as long as phase B & C are the same.
- Phase A =OK to have 2 conductors but both must be identical and Phase B & C must be the same.
Rgds,
Eskim
RE: Paralleling Different Cable size
xnuke
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