Unique underground power line would send renewable energy from Midwest to Eastern markets

[hunter]

7. Simple explanation: Water and wet earth conduct electricity.

In a buried or underwater HVAC power line the electric current moves from positive to negative at fifty or sixty cycles per second. This creates a fluctuating electromagnetic field that induces electric currents in the water or soil surrounding the line, wasting energy.

The problem isn't so pronounced in cables strung from towers.

HVAC lines on towers can carry power for hundreds of miles with acceptable losses, but just tens of miles underground or under water.

In an HVDC power line the electromagnetic field doesn't fluctuate so long as the power going through the line is constant. Currents that don't fluctuate don't generate electric currents in the surrounding medium.

HVDC lines can carry power for hundreds of miles under ground or under water, and a few thousand miles on towers.

It is of course more complicated than that -- all about resistance, capacitance, inductance, impedance, insulation, inverse square laws, etc. -- but that's the gist of it.

The safety aspects of an underground HVDC line are similar to large high pressure gas lines. There's a lot of potential energy in a fully charged HVDC line. It's not something you'd want to hit with a back hoe.