ABB Relion 670 series, Техническое руководство, Страница: 134 / 1432

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-US
Figure 36: Description of the restrained, and the unrestrained operate characteristics
where:
100%
Ioperate
slope
Irestrain
D
= D ×
EQUATION1246 V1 EN-US
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.
Section 1: This is the most sensitive part on the characteristic. In section 1, normal currents flow
through the protected circuit and its current transformers, and risk for higher false differential
currents is relatively low. An un-compensated on-load tap-changer is a typical reason for existence
of the false differential currents in this section. The slope in section 1 is always zero percent.
Section 2: In section 2, a certain minor slope is introduced which is supposed to cope with false
differential currents proportional to higher than normal currents through the current
transformers.
Section 6 1MRK 502 066-UUS B
Differential protection
128
Technical manual