Section 1
UnrestrainedLimit
Section 2
Section 3
Restrain
Operate
unconditionally
5
4
3
2
1
0
0 1 2 3 4 5
IdMin
EndSection1
EndSection2
Restrain current
[ in pu of IBase]
Operate current
[ in pu of IBase]
SlopeSection2
SlopeSection3
en05000300.vsd
Operate
conditionally
IdMinHigh
A
C
B
IEC05000300 V1 EN-US
Figure 34: Description of the restrained and the unrestrained operate
characteristics
where:
100%
Ioperate
slope
Irestrain
D
=
D
×
EQUATION1246 V1 EN-US
and where the restrained characteristic is defined
by the settings:
1. IdMin
2. EndSection1
3. EndSection2
4. SlopeSection2
5. SlopeSection3
The second analysis is the 2
nd
and 5
th
harmonic analysis of the three instantaneous
differential currents. Occurrence of these harmonics over a level that is set
separately for each one blocks tripping action from the biased slope evaluation.
Section 6 1MRK 505 394-UEN A
Differential protection
96 Line differential protection RED650 2.2 IEC
Technical manual
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