ABB RELION 620 Series Technical Manual page 441

1MAC504801-IB E
620 series ANSI
Technical Manual
If the biasing current is small compared to differential current, or if the phase angle
between the current of two windings with the highest phase current is close to zero
(normally, the phase difference is 180 degrees) or the phase angle between the compared
phase currents (in case of two winding transformer) is close to zero, a fault has occurred
in the area protected by the differential protection. Then the trip value set for the
instantaneous stage is automatically halved and the internal blocking signals of the biased
stage are inhibited.
Id/Ir
High trip value
TRIP AREA (LS)
Slope
section 2
Low trip value
End section 1
GUID-E15E6D41-4FDA-4701-A902-EE372C7C8B0F V1 EN
Figure 200: Operating characteristics of the protection. LS stands for Biased low
stage and HS for Instantaneous high stage.
The TRIP output is always activated with the OPR_HS output. The internal blocking
signals of the differential function do not prevent the operating signal of the instantaneous
differential current stage from being activated. When required, the trip outputs of
Instantaneous high stage can be blocked by the external control signals BLK_OPR_HS or
BLOCK.
TRIP AREA (HS)
Slope
section 3
NON-TRIP AREA (LS & HS)
End section 2
Section 4
Protection functions
NON-TRIP AREA (LS)
Ib/Ir
435