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Q&A Would we need Alternating Current if superconducting wires existed?

posted over 1 year ago by celtschk‭  ·  edited over 1 year ago by celtschk‭

Answer
#2: Post edited by user avatar celtschk‭ · 2021-02-14T20:36:17Z (over 1 year ago)
  • The major advantage of AC is that is can be easily transformed to different voltages. This is important because current transport is most efficient if the currents are low (because the losses are proportional to the square of the current), and this is achieved by making the voltage high for transmission (the transmitted power is the product of current and voltage; by making the voltage higher, you need less current to transmit the same power). On the other hand we don't want very high voltage at the point of use (because high voltage is dangerous, no matter whether AC and DC).
  • Actually for the transport itself, DC would be better (however AC power transmission networks use the frequency to guide the power generation; when using DC, this has to be replaced by a separate mechanism).
  • Now the question is what would change if we had practicable superconducting wires.
  • It would be even more important to send only small currents. This is because superconductors lose their superconductivity if the current gets too large. However type II superconductors (this is the type which has high critical temperatures, and therefore is the one you'd expect in superconducting wires) [exhibit losses under AC current,](https://indico.cern.ch/event/440690/contributions/1089769/attachments/1148950/1648370/U7-final.pdf) and since lossless current transport is the whole point of using superconducting wires for power transmission, this means we would likely use high voltage DC transmission.
  • The major advantage of AC is that is can be easily transformed to different voltages. This is important because current transport is most efficient if the currents are low (because the losses are proportional to the square of the current), and this is achieved by making the voltage high for transmission (the transmitted power is the product of current and voltage; by making the voltage higher, you need less current to transmit the same power). On the other hand we don't want very high voltage at the point of use (because high voltage is dangerous, no matter whether AC or DC).
  • Actually for the transport itself, DC would be better (however AC power transmission networks use the frequency to guide the power generation; when using DC, this has to be replaced by a separate mechanism).
  • Now the question is what would change if we had practicable superconducting wires.
  • It would be even more important to send only small currents. This is because superconductors lose their superconductivity if the current gets too large. However type II superconductors (this is the type which has high critical temperatures, and therefore is the one you'd expect in superconducting wires) [exhibit losses under AC current,](https://indico.cern.ch/event/440690/contributions/1089769/attachments/1148950/1648370/U7-final.pdf) and since lossless current transport is the whole point of using superconducting wires for power transmission, this means we would likely use high voltage DC transmission.
#1: Initial revision by user avatar celtschk‭ · 2021-02-14T20:27:29Z (over 1 year ago)
The major advantage of AC is that is can be easily transformed to different voltages. This is important because current transport is most efficient if the currents are low (because the losses are proportional to the square of the current), and this is achieved by making the voltage high for transmission (the transmitted power is the product of current and voltage; by making the voltage higher, you need less current to transmit the same power). On the other hand we don't want very high voltage at the point of use (because high voltage is dangerous, no matter whether AC and DC).

Actually for the transport itself, DC would be better (however AC power transmission networks use the frequency to guide the power generation; when using DC, this has to be replaced by a separate mechanism).

Now the question is what would change if we had practicable superconducting wires.

It would be even more important to send only small currents. This is because superconductors lose their superconductivity if the current gets too large. However type II superconductors (this is the type which has high critical temperatures, and therefore is the one you'd expect in superconducting wires) [exhibit losses under AC current,](https://indico.cern.ch/event/440690/contributions/1089769/attachments/1148950/1648370/U7-final.pdf) and since lossless current transport is the whole point of using superconducting wires for power transmission, this means we would likely use high voltage DC transmission.