ABB RELION REX640 Technical Manual page 506

Section 4
Protection functions
500
Forward area
RCA = -90˚
Maximum torque line
Io (Operating quantity)
Forward area
GUID-519B6485-D523-4A25-A4EE-8BAAEB3D1F5D V1 EN
Figure 274: Definition of relay characteristic angle, RCA = -90° in an isolated
network
Characteristic angle should be set to a positive value if the operating
signal lags the polarizing signal and to a negative value if the
operating signal leads the polarizing signal.
Type of network
Compensated network
Unearthed network
In unearthed networks, when the characteristic angle is -90°, the
measured residual power is reactive (varmetric power).
The fault direction is also indicated FAULT_DIR (available in the monitored data
view), which indicates 0 if a fault is not detected, 1 for faults in the forward direction
and 2 for faults in the backward direction.
The direction of the fault is detected only when the correct angle calculation can be
made. If the magnitude of the operating quantity or polarizing quantity is not high
enough, the direction calculation is not reliable. Hence, the magnitude of the operating
quantity is compared to the Min operate current setting and the magnitude of the
polarizing quantity is compared to Min operate voltage, and if both the operating
quantity and polarizing quantity are higher than their respective limit, a valid angle is
calculated and the residual power calculation module is enabled.
The Correction angle setting can be used to improve the selectivity when there are
inaccuracies due to the measurement transformer. The setting decreases the operation
-Uo (Polarizing quantity)
Backward area
Minimum
operate current
Backward area
Recommended characteristic angle
0°
-90°
1MRS759142 C
REX640
Technical Manual