Functions
2.14 Differential Protection and Its Protected Objects
SIPROTEC, 7UM62, Manual
C53000-G1176-C149-7, Release date 03.2010
109
Figure 2-37 Increase of pickup value for stage I
DIFF>
on startup
Fault Detection, Dropout
The differential protection does not normally use a "pickup", since the detection of a fault is identical with the
tripping condition. Like all SIPROTEC 4 devices, however, the differential protection feature of the 7UM62 has
a pickup that is the starting point for a number of subsequent activities. The pickup marks the beginning of a
fault. This is necessary e.g. for creating fault logs and fault records. The pickup also controls internal function
sequences for both internal and external faults (such as necessary actions of the saturation detector).
A pickup is detected as soon as the fundamental wave of the differential current has attained 85 % of the setting
value or more than 85 % of the stabilizing current are in the add-on stabilization area (see following figure). A
pickup signal is also issued when the high-speed trip stage for high-current faults picks up.
Figure 2-38 Pickup of the Differential Protection
If stabilization by higher-order harmonics is activated, the system first performs a harmonic analysis (approx. 1
cycle) to check the stabilization conditions if necessary. Otherwise, the trip command is issued as soon as the
tripping conditions are fulfilled (hatched area in Figure 2-33).
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