Section 4
1MAC050144-MB C
Protection functions
326
615 series ANSI
Technical Manual
Figure 154:
Operating characteristic for the restrained differential protection function
When the differential current exceeds the operating value determined by the operating
characteristics, the OPR_LS output is activated. The TRIP output is always activated when
the OPR_LS output activates.
The trip signal due to the biased stage can be blocked by the activation of the
BLK_OPR_LS or BLOCK input. Also, when the operation of the biased low stage is
blocked by the waveform blocking functionality, the INT_BLKD output is activated
according to the phase information.
The phase angle difference between the two currents I_A1 and I_A2 is theoretically 180
electrical degrees for the external fault and 0 electrical degrees for the internal fault
conditions. If the phase angle difference is less than 50 electrical degrees or if the biasing
current drops below 30 percent of the differential current, a fault has most likely occurred
in the area protected by 87M. Then the internal blocking signals (CT saturation and DC
blocking) of the biased stage are inhibited.
I
b2
I
d1
I
d2
I
b3
I
d3
TRIP
NON TRIP
100
200
300
100
200
300
400
500
End section 2
End section 1
Low trip value
Section 1
Section 2
Section 3
I
b
[%In]
I
d
[%In]
Содержание 615 Series ANSI
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Страница 707: ...Section 15 1MAC050144 MB C Applicable standards and regulations 700 615 series ANSI Technical Manual ...
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