Definite Time, Directional High-Set Current Element 67N-2 - Siemens SIPROTEC 7SK80 Manual

Functions
2.3 Directional Gound Overcurrent Protection 67N
2.3.2 Definite Time, Directional High-set Element 67N-2
Each ground current is compared with the pickup value 67N-2 PICKUP. Currents above the setting values are
recognized searately when fault direction is equal to the configured direction. After the corresponding delay
time 67N-2 DELAY has expired, the trip command is issued. The dropout value is roughly equal to 95% of the
pickup value for currents > 0.3 I
The pickup can be prolonged additionally via the configurable dropout time 1618 67N T DROP-OUT. This time
is started and maintains the pickup condition if the current falls below the threshold. Therefore, the function
does not drop out at high speed. Meanwhile, the trip command delay time 50N-2 DELAY continues running.
After the dropout delay time has elapsed, the pickup is reported OFF and the trip delay time is reset unless the
threshold 50N-2 PICKUP has been exceeded again. If the threshold is exceeded again during the dropout
delay time, the time is cancelled. The trip command delay time 50N-2 DELAY continues running. If the thresh-
old value is exceeded after this time has elapsed, the trip command is issued immediately. If the threshold value
is not exceeded at this time, there is no reaction. If the threshold value is exceeded again after the trip command
delay time has elapsed and while the dropout delay time is still running, tripping will be initiated immediately.
The following figure shows the logic diagram for the high current element 67N-2 of the ground currents.
Figure 2-17 Logic diagram of the directional element 67N-2
80
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Nom
SIPROTEC, 7SK80, Manual
E50417-G1140-C344-A4, Release date 08.2010