Schweitzer Engineering Laboratories SEL-311C - Figure 3.2 Compensator-Distance Phase-To-Phase Element Operation

3.4
SEL-311C Relay Instruction Manual Date Code 20060320
Distance, Out-of-Step, Overcurrent, Voltage, Synchronism Check, and Frequency Elements
Distance Elements
Note: V
A
, V
B
, and V
C
are internal element voltages, not system voltages.
Figure 3.2 Compensator-Distance Phase-to-Phase Element Operation
V
B
V
B
V
B
V
B
Unfaulted
V
A
V
A
V
A
V
A
V
C
V
C
V
C
V
C
Fault Near Balance Point
Forward External Fault
Internal Fault
V
BC
– Z • I
BC
V
BC
– Z • I
BC
V
BC
– Z • I
BC
V
BC
– Z • I
BC
V
AB
– Z • I
AB
V
AB
– Z • I
A
B
V
AB
– Z • I
AB
V
AB
– Z • I
AB
Test Angle θ <180˚
sin (θ) > 0
Test Angle θ <180˚
sin (θ) > 0
Test Angle θ > 180˚
sin (θ) < 0
Test Angle θ <180˚
sin (θ) > 0