Answer / krishna rao vutukuru

distance protection can be done in 3 ways by measuring
1)impedance method(impedance relay)
2)reactance method(reactance relay)
3)admittance method(mho relay)

reactance relay used for detection of earth faults(since it is indepedant of ground resistance)

mho relay is used for protection of long transmisson lines(since it is less affected by power swings)

impedance relay is used for protection of medium lenghth transmisson lines.

Answer / nirujogi suresh

reactance relay is less affected by power swings as it is response to only for grounded faults

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