Section 1
Operate
conditionally
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
[ times IBase ]
operate current
[ times IBase ]
SlopeSection2
SlopeSection3
en05000187-2.vsd
IEC05000187 V2 EN
Figure 32:
Description of the restrained, and the unrestrained operate
characteristics
where:
100%
Ioperate
slope
Irestrain
D
= D
×
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 reset ratio is in all parts of the characteristic equal to
0.95.
Section 1
: This is the most sensitive part on the characteristic. In section 1, normal
currents flow through the protected object and its current transformers, and risk for higher
false differential currents is relatively low. An un-compensated on-load tap-changer is a
Section 6
1MRK 502 048-UUS A
Differential protection
100
Technical manual
