How Do You Derive the Equation for a Medium-Distance Power Transmission Line?

[MissP.25_5]

Hello.
I need to derive this equation (attached), can you help me please?

That's the equation for a two-pair terminal medium-distance power transmission line (20~100km).
I have no idea how to start it. Can someone guide me, please?

 

[NascentOxygen]

Hi MissP.25_5. Perhaps a clue lies in that bottom line.

Try a Pi network, with the two vertical limbs each a capacitor, and the horizontal part R + L.

So this leaves the Earth as a straight-through link common to both ports.

Note, I haven't examined this further.

 

[MissP.25_5]

Hi MissP.25_5. Perhaps a clue lies in that bottom line.

Try a Pi network, with the two vertical limbs each a capacitor, and the horizontal part R + L.

So this leaves the Earth as a straight-through link common to both ports.

Note, I haven't examined this further.

Oh, yes! That's right, the Pi network is the solution! I just solved it, thanks to you!

 

[NascentOxygen]

Oh, yes! That's right, the Pi network is the solution! I just solved it ...

Glad it worked! http://imageshack.com/a/img593/2259/girlpower.gif