What is the distribution voltage in electricity transmission?

Every conductor (in this case, the transmission line) has a finite resistance. so for example let us say it has a resistance of 1 ohm over a distance of 1 km. then, if the current through the conductor is say 100 Amperes, you will have a voltage drop of 100 volts across a length of 1 km.

So, a line carrying 100 Amps at 25 kV will have an effective voltage of 24.9 kV