Minimizing overeaching in Impedance relays by limiting restive reach

[warickwrx]

Hi

I am looking for some information and perhaps reasons why one would use the following criterion to limit restive reaches to mitigate overreaching in an Impedance relay's

For earth faults the resistive Zone 1 reach is limited by 4.5 <= X1

For phase-to-phase resistive reach of Zine 1 is limited by 3 <= X1

regards