ABB RELION REX640 Technical Manual page 682

Protection functions
TAP_POS
BLK_OPR_HS
BLK_OPR_LS
Figure 387: Functional module diagram
Differential calculation
TR2PTDF operates phase-wise on a difference of incoming and outgoing currents.
The positive direction of the currents is towards the protected object.
Figure 388: Positive direction of the currents
I
=
d
In a normal situation, no fault occurs in the area protected by TR2PTDF. Then
the currents I
practice, however, the differential current deviates from zero in normal situations.
In the power transformer protection, the differential current is caused by CT
682
I_A1
I_B1
I3P1
I_C1
I_A2
I_B2
I3P2
I_C2
BLOCK
I
W 1
Winding 1
(usually HV)
I I
+
W W
1 2
and I
W1 W 2
Differential
calculation
Transformer
vector group
matching
Zero-sequence
component
elimination
Compensation
of tap changer
position
Second
harmonic
blocking
Fifth harmonic
blocking
Waveform
blocking
Winding 2
(usually LV)
are equal and the differential current I
1MRS759142 F
Instantaneo
us high
OR
stage
Biased
low stage
I
W 2
(Equation 157)
is zero. In
d
Technical Manual
OPERATE
OPR_HS
OPR_LS
BLKD2H
BLKD5H
BLKDWAV
REX640