ABB RELION 620 Series Technical Manual page 440

Section 4
Protection functions
434
Low
trip
Curve
value
I [%I ]
d r
1 50 %Ir
2 20 %Ir
300
3 5 %Ir
200
100
100
GUID-8BDD4422-013A-4CE3-9282-8614296B4F45 V1 EN
Figure 199: Setting range for Biased low stage
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 most
certainly occurred in the area protected by the differential protection relay. The internal
blocking signals of the biased stage are inhibited.
The operation of the differential protection is based on the fundamental frequency
components. The operation is accurate and stable: the DC component and harmonics of
the current do not cause unwanted operations.
Instantaneous high stage
Instantaneous high stage can be enabled or disabled with the Enable high set setting. The
corresponding parameter values are "True" and "False".
The operation of Instantaneous high stage is not biased. The instantaneous stage trips and
the OPR_HS output is activated when the amplitude of the fundamental frequency
component of the differential current exceeds the set operation value High trip value or
when the instantaneous value of the differential current exceeds 2.5 x High trip value. The
value 2.5 (=1.8 x √2) is due to the maximum asymmetric short circuit current.
Slope End
section
section
2 2
50 % 100 %Ir
30 % 150 %Ir
10 % 500 %Ir
Curve 1
Curve 2 ( Default settings )
Curve 3
200 300
1MAC504801-IB E
400 500 I [%I ]
d r
620 series ANSI
Technical Manual