ABB REG670 Technical Manual page 130

Section 6
Differential protection
124
1. IdMin
2. EndSection1
3. EndSection2
4. SlopeSection2
5. SlopeSection3
operate current
[ times IBase ]
5
4
3
2
1
IdMin
0
0
EndSection1
IEC05000187 V2 EN
Figure 33: Description of the restrained, and the unrestrained operate
characteristics
where:
D
Ioperate
= ×
slope
100%
D
Irestrain
EQUATION1246 V1 EN
The operate - restrain characteristic is tailor-made and can be designed freely by the
user after his needs. The default characteristic is recommended to be used. It gives
good results in a majority of applications. The operate - restrain characteristic has in
principle three sections with a section-wise proportionality of the operate value to the
bias (restrain) current. The reset ratio is in all parts of the characteristic equal to 0.95.
Operate
unconditionally
UnrestrainedLimit
Operate
conditionally
Section 1
Section 2
SlopeSection2
1 2
EndSection2
1MRK502052-UEN B
Section 3
SlopeSection3
Restrain
3 4 5
restrain current
[ times IBase ]
en05000187-2.vsd
Technical manual