Correct option is D
For short transmission lines, a reactance relay is used, for medium transmission lines, an impedance relay is used, and for long transmission lines, a Mho relay is preferred.
Explanation:
Reactance relay: This relay is suitable for short lines because it is less affected by arc resistance, which is a significant factor in short line faults.
Impedance relay: This relay is considered appropriate for medium length lines as it provides a balance between the characteristics of short and long lines.
Mho relay: For long transmission lines, a Mho relay is preferred due to its ability to handle power swings and provide accurate fault location.
