Protection Engineering Basics and Schemes Protection Engineering | Page 122

5.3.4 Directional Overcurrent Relay(67)
In directional overcurrent relay, angle between two
different quantities are measure and relay acted when
angle between quantities reached at pick up values.
Main application of this relays are in ring system, where
multiple source of power is supplying power to different
branches of loads.
Some possible connections are shown below
Relay will activate from angular region where current
leads voltage by 30 degree and lag voltage by 150 degree,
it is tripping zone of this type of connection.
One more setting type is given below
pg. 122