Connecting transmission lines

[gank]

Hi everybody!
I'm modeling MV lines as electrical long lines, by means of transmission lines equations. I want to connect the lines to a current source. I'm thinking about using the Chain parameters representation. My problem is how to represent an active network like a current source so as to connect it to the line?
I found an interesting approach in Paul's book "Analysis of multiconductors lines", but I have some trouble with it. Anyone used it?

Thanks a lot for all your comments