Cable selection based on current 1

[mielke]

Hello, hoping to be pointed towards anything on the topic of power transmission selection based on current levels. I’m familiar with changing wire gauge size based on higher current, but at what point do different power transmission methods start to make commercial sense? For example when do bus bars, cooled cables, or anything other start making sense? Thinking in terms of 1kA, 10kA, etc DC

Thanks!

 

[wcaseyharman]

Nothing official, but it seems at the medium voltage level that I am familiar with once you get more than a few thousand amps of load current cables get unwieldy. Most of the power plants with load currents above 2500A use some sort of bus rather than cables, I assume it’s a price and space decision as there is some overlap.

 

[Gr8blu]

In addition to simple ampacity several other factors should be examined: ambient temperature, altitude, proximity to other conductors, type of cooling, type of insulation, and exposure to contamination. All have an effect on the "when do I switch" question.

In general terms, if the conductor needs moderate flexibility the upper limit is around 1000 A at max 40 C ambient and 1000 m. As currents get higher (or more derating factors are employed), multiple conductors are used in parallel. At some point, the bundle gets too unwieldy (or the proximity factor causes too much derating) and the switch is made to bus.

Converting energy to motion for more than half a century

 

[waross]

Inter-connections, such as switch yards and substations are mostly bus. There are exceptions.
Transmission for any distance is cables.
We did use cables in buried duct to feed an additional switch line up in an underground sub.
Copper conductor, paper insulated, lead sheathed, PVC jacketed cable.
3600 MCM, fed by a 6000 Amp breaker.
3600 MCM, Yes 3.6 square inches cross section cable.
ps: single conductor.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!