ABB RELION Series Technical Manual page 370

Section 4
Protection functions
364
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
sector. The Correction angle setting should be done carefully as the phase angle error
of the measurement transformer varies with the connected burden as well as with the
magnitude of the actual primary current that is being measured. An example of how
Correction angle alters the operating region is as shown:
Zero torque line
Correction angle
operate current
Backward
GUID-B420E2F4-8293-4330-A7F3-9A002940F2A4 V1 EN
Figure 191: Definition of correction angle
The polarity of the polarizing quantity can be changed (rotated by
180°) by setting Pol reversal to "True" or by switching the polarity of
the residual voltage measurement wires.
Residual power calculation
The Residual power calculation module calculates the magnitude of residual power
3UoIoCosφ. Angle φ is the angle between the operating quantity and polarizing
quantity, compensated with a characteristic angle. The angle value is received from
the Directional calculation module. The Directional calculation module enables the
residual power calculation only if the minimum signal levels for both operating
quantity and polarizing quantity are exceeded. However, if the angle calculation is not
valid, the calculated residual power is zero. Residual power (RES_POWER) is
Maximum torque line
forward direction (RCA = 0˚)
-Uo (Polarizing quantity)
Io (Operating quantity)
Forward
area
Minimum
Backward
area
1MRS758755 A
Forward
area
Correction angle
area
REC615 and RER615
Technical Manual