Power Transformer In The Protected Zone - ABB RELION 650 Series Applications Manual

1MRK 505 363-UEN A
If one or the
other of
currents is too
low, then no
measurement
is done, and
120 degrees
is mapped
180 deg
External
fault
region
IEC05000188 V3 EN-US
Figure 42: Negative sequence current function Relay Operate Angle (ROA)
IminNegSeq
IminNegSeq is set as a multiple of IBase . The local, and the sum of all remote negative
sequence currents are compared separately if they are above the set threshold value
IminNegSeq . If either is below the threshold, no comparison is made. Neither internal nor
external fault is declared in this case. The default value 0.04 ×
considerations, such as extremely week sources, are taken into account. Observe that
internally, whenever the bias current is higher than 1.5 times
equal to the sum of
internal/external fault discriminator under heavy three-phase external fault conditions with
severe CT saturation.
6.2.3.5

Power transformer in the protected zone

One three-winding transformer or two two-winding transformers can be included in the line
protection zone. The parameters below are used for this purpose. The alternative with one
two-winding transformer in the protected zone is shown in figure
RED
670
IEC05000442 V1 EN-US
Figure 43: One two–winding transformer in the protected zone (example showing 670
Application manual
90 deg
120 deg
270 deg
IminNegSeq + 0.1 Ibias . This is in order to prevent wrong decisions of the
device)
Internal/external
fault boundary
NegSeqROA
Operate
IMinNegSeq
en05000188-3-en.vsd
Protected zone
Differential protection
(Relay
Angle)
0 deg
Internal
fault
region
IBase can be used if no special
IBase , the actual threshold is
43 and figure 44.
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en05000442.vsd
Section 6
M12541-223 v4
M12541-6 v6
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