Siemens 7UT51

7UT51 v3
Motor or Generator Differential Protection (87M/G)
5
PRIM-2330C 73
Figure 5.3 Differential Protection Characteristic for a Motor or Generator
1
2
3
4
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Non-Operate Area
Slope 1 (1706)
Slope 2 ( base point = 1707, slope = 1708 )
7UT51
5
6
7
8
Operate Area
0
0
9
87M Min
(1703)
G/M
Through-Fault Restraint Area
( slope = 1/2 of 1706, left edge = 1718,
duration = 1717 )
Restraining Current, ( in multiples of )I
rest
I
n
Differential Current, ( in multiples of )I
diff
I
n
I=
diff
I
rest
I
diff
=
′
+
′
II
12
I
rest
=
′
+
′
II
12
′
I
1
′
I
2