AC superconductor transmission

[kevinisfrom]

TL;DR Summary

For underground AC transmission, the line charging current prevents the lines from exceeding 100 km due to the close proximity and high capacitance between the line and ground. If the line was made with superconducting material, I think the same distance limitation applies (assuming same power and voltages). The only saving grace I can see is that due to the higher currents, the voltages can be reduced, thus less effect of line charging and potentially longer lines.

For underground AC transmission, the line charging current prevents the lines from exceeding 100 km due to the close proximity and high capacitance between the line and ground. If the line was made with superconducting material, I think the same distance limitation applies (assuming same power and voltages). The only saving grace I can see is that due to the higher currents, the voltages can be reduced, thus less effect of line charging and potentially longer lines. Wanted to check and see if this rough understanding makes sense to the community?

 

[anorlunda]

It works. Some pilot cables are in use.

The challenge, above ground or below is the power to keep it cold compared with the power saved by zero resistive losses.

Underground cables have other unique risks. Floods are a big one. Heat baking is another. The city of Aukland NZ was blacked out when hot weather baked all the underground cables bringing power into the city.

Good thinking by the way. Line to ground capacitance is indeed a major limitation of underground AC cables. We might reduce that somewhat with super conducting cables. But maybe not enough to matter. Depends on the details.

 

[Baluncore]

The only saving grace I can see is that due to the higher currents, the voltages can be reduced, thus less effect of line charging and potentially longer lines.

As current in a superconductor increases there are two limitations. The first is that there is a critical current density at which the superconductivity ceases. That is of the order of about 10⁵ A/cm².
The second is that the current flowing when superconductivity is suddenly lost, can generate sufficient heat to vaporise the superconductive material.