ABB RELION REX640 Technical Manual page 718

Protection functions
TAP_POS
BLK_OPR_HS
BLK_OPR_LS
Figure 406: Functional module diagram
Differential calculation
TR3PTDF operates phasewise on the difference of incoming and outgoing currents.
The positive direction of the currents is towards the protected object.
Figure 407: Single-line diagram of the positive direction of the currents in a
threewinding transformer
The normalized amplitude of the differential current per phase Id is obtained using
the equation:
718
I_A1
I_B1
I3P1
I_C1
I_A2
I_B2
I3P2
I_C2
I_A3
I_B3
I3P3
I_C3
BLOCK
I
W 1
Differential
calculation
Transformer
vector group
matching
Zero-sequence
component
elimination
Compensation
of tap changer
position
Second
harmonic
blocking
Fifth harmonic
blocking
Waveform
blocking
Winding 1
(usually HV)
1MRS759142 F
Instantaneo
us high
OR
stage
Biased
low stage
Winding 3
(usually tertiary)
I
W 3
I
W 2
Winding 2
(usually LV)
Technical Manual
OPERATE
OPR_HS
OPR_LS
BLKD2H
BLKD5H
BLKDWAV
REX640