Mho characteristics is good for phase-phase faults but it is not suitable for phase-earth fault and specially with high fault resistance and arcing resistance.
Quadrilateral characteristics with their availabilities to be increased only in one direction (R or X) is used to over come the problem of high resistance fault. For each stage of distance relay the characteristics can be extended only in R direction with fixed X setting.
Figure (26) shows a four stage quadrilateral distance relay characteristics. For that relay zones 1, 2, and 3 are in the forward direction and zone 4 in the reverse direction.
