ABB RELION 620 Series Technical Manual page 464

Section 4
Protection functions
458
coil sometimes is temporarily disconnected. When the coil is disconnected, the
compensated network becomes isolated and the Characteristic angle setting must be
changed. This can be done automatically with the RCA_CTL input, which results in
the addition of -90° in the Characteristic angle setting.
The value (ANGLE_RCA) is available in the monitored data view.
Forward area
RCA = -90˚
Maximum torque line
Io (Operating quantity)
Forward area
GUID-AA58DBE0-CBFC-4820-BA4A-195A11FE273B V1 EN
Figure 231: 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
-Uo (Polarizing quantity)
Backward area
Minimum
operate current
Backward area
Recommended characteristic angle
0°
-90°
1MRS757644 F
620 series
Technical Manual