ABB RELION REX640 - Page 682

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