Functions
2.3 Directional Gound Overcurrent Protection 67N
SIPROTEC, 7SK80, Manual
E50417-G1140-C344-A4, Release date 08.2010
81
If parameter 1613 is set to 67N-2 instant. and manual close detection applies, the trip is initiated as soon
as the pickup conditions arrive, even if the element is blocked via a binary input.
2.3.3 Definite Time, Directional Overcurrent Element 67N-1
The ground current is compared with the setting value 67N-1 PICKUP. Currents above the setting values are
recognized separatly when fault direction is equal to the configured direction. If the inrush restraint feature is
used, either the normal pickup signals or the corresponding inrush signals are issued as long as inrush current
is detected. When the corresponding delay time 67N-1 DELAY has expired, a trip signal is issued unless an
inrush has been recogniszed or inrush restraint is active. If an inrush condition is detected while the inrush re-
straint function is enabled, there will be no trip but a message will be generated indicating that the timer has
elapsed. Trip signals and timer runout messages are available separately for each element. The dropout value
is roughly equal to 95% of the pickup value for currents > 0.3 I
Nom
.
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-1 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-1 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-1 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 inrush restraint of the overcurrent element 50N-1 PICKUP is disabled via configurable dropout times if an
inrush pickup occurs because the presence of an inrush does not constitute an intermittent fault.
The following figure shows the logic diagram for the directional overcurrent element 67N-1 of the ground cur-
rents.
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