ABB RELION REX640 Technical Manual page 610

Section 4
Protection functions
604
GUID-606FA7E6-185B-4515-AE35-37A2314AEF81 V1 EN
Figure 334: Setting range for biased low stage
If the biasing current is small compared to the differential current of the phase angle
between the winding 1 and winding 2 phase currents is close to zero (in a normal
situation, the phase difference is 180 degrees), a fault has most likely occurred in the
area protected by TR2PTDF. Then the internal blocking signals of the biased stage are
inhibited.
Instantaneous high stage
The instantaneous high stage operation can be enabled and disabled with the Enable
high set setting. The corresponding parameter values are "TRUE" and "FALSE."
The operation of the instantaneous high stage is not biased. The instantaneous stage
operates and the output OPR_HS is activated when the amplitude of the fundamental
frequency component of the differential current exceeds the set High operate value or
when the instantaneous value of the differential current exceeds 2.5 times the value of
High operate value. The factor 2.5 (=1.8 × √2) is due to the maximum asymmetric
short circuit current.
If the biasing current is small compared to the differential current or the phase angle
between the winding 1 and winding 2 phase currents is close to zero (in a normal
situation, the phase difference is 180 degrees), a fault has occurred in the area
protected by TR2PTDF. Then the operation value set for the instantaneous stage is
automatically halved and the internal blocking signals of the biased stage are
inhibited.
1MRS759142 C
REX640
Technical Manual