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Functions
2.3 Directional Overcurrent Protection Ground 67, 67N
2.3.2
Directional Definite Time High-Current Elements 67N-2, 67N-3
Each ground current is compared with the pickup value 67N-2 PICKUP or 67N-3 PICKUP. Currents above
the setting values are reported provided that the fault direction is the same as the configured direction. After
expiry of the respective delay time 67N-2 DELAY or 67N-3 DELAY, the trip command is issued. The dropout
value is approximately 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 instantaneously. The trip-command delay time 50N-2 DELAY or 67N-3 DELAY continues
running in the meantime. 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 or 67N-3 PICKUP has been violated again. If the threshold
is exceeded again during the dropout delay time, the time is canceled. However, the trip command delay time
50N-2 DELAY or 67N-3 DELAY continues running. If the threshold 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 expiry of the trip command delay time, while the dropout
delay time is still running, tripping is initiated immediately.
The element can work directionally or non-directionally.
The following figure shows the logic diagram for the high current element 67N-2 of the ground currents. The
high-current element 67N-3 is structured identically.
88
.
Nom
SIPROTEC, 7SK80, Manual
E50417-G1140-C344-A5, Release date 11.2012
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