cst- how look at the impedance of distance ?

cst- how look at the impedance of distance ?

power voltage( 500V, 20A) source put into a long cooper bar

then, other PCB plate sense a voltage level (according to distance 1mm~100mm)

example ) when 500volt put into cooper bar, PCB plate sense 0.1Volt. so 1/5000

i quest)

1. how can source port give?
2. how see coupling level?
3. last, how can see impedance of distance i want to serch 50ohm distance .