When ground fault occurs on transmission lines how would we determine on which area the fault is occurred and what parameters help to determine that?

In transmission protection system we generally Distance protection

to detect & safguard to enhance system. Considering the total ditance

we saperate into different Zones, like Z1 covers 1st 50 %, Z2 covers 50-100 % 

distance, Z3 covers -10% distance. Say Z1(Impedence) = 290 Ohm, in case fault

Z1 value will differ with orizinal value, when it reaches trip value Distance relay will

operate.