ABB REG670 Technical Manual page 143

1MRK502052-UEN B
Technical manual
1. Instantaneous values of currents (samples) from the HV, and LV sides for two-
winding power transformers, and from the HV, the first LV, and the second LV
side for three-winding power transformers.
2. Currents from all power transformer sides expressed as fundamental frequency
phasors with their real and imaginary parts. These currents are calculated within
the protection function by the fundamental frequency Fourier filters.
3. Negative sequence currents from all power transformer sides expressed as
phasors. These currents are calculated within the protection function by the
symmetrical components module.
The power transformer differential protection:
1. Calculates three fundamental frequency differential currents and one common
bias current. The zero-sequence component can optionally be eliminated from
each of the three fundamental frequency differential currents and at the same time
from the common bias current.
2. Calculates three instantaneous differential currents. They are used for harmonic,
and waveform analysis. Instantaneous differential currents are useful for post-
fault analysis using disturbance recording
3. Calculates negative-sequence differential current. Contributions to it from both
(all three) power transformer sides are used by the internal/external fault
discriminator to detect and classify a fault as internal or external.
BLKUNRES
a
IdUnre
b
IDL1MAG
IBIAS
BLOCK
BLKRES
IDL1
2nd
Harmonic
Wave
block
5th
Harmonic
Cross Block
from L2 or L3
OpCrossBlock=On
IEC06000545 V1 EN
Figure 39: Transformer differential protection simplified logic diagram for Phase
L1
b>a
AND
OR
AND
Section 6
Differential protection
TRIPUNREL1
AND
TRIPRESL1
AND
1
Cross Block
to L2 or L3
AND
OR
en06000545.vsd
STL1
BLK2HL1
BLKWAVL1
BLK5HL1
137