[TowerTalk] Measuring voltage along an element

[Denis Coolican]

Possibly someone can help.

I am building/designing a 2 element 80m Yagi with elements that can be adjustable in length.  The elements will have a total length of 100 ft and as such I do have a loading coil of about 15 microhenries in each half of the element.  The coil and the element length adjustment mechanism is located at the center of the element.

Since the elements are so long and are adjustable I have a triangular structure that goes out for 30 ft from the center to support each side of the elements. The structure will be at ground potential.  I realize that the voltage across the coil will be high for an air coil (about 3.5 KV at rated power levels). 
I can see what the magnitude of the currents are but I would like to be able to calculate or estimate what the voltage is between the element and the structure (ground) such that I can make sure I have the correct amount of insulation. 

I do not see anything in the handbooks on this subject.  I was wondering if anyone can help.

Denis ve6aq with ve6fi