Definite Time High-Set Elements 50-3, 50-2, 50N-3, 50N-2 - Siemens SIPROTEC 7SK80 Manual
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The following table gives an overview of the interconnection to other functions of 7SK80.
Table 2-2
Overcurrent protection elements
50-1
50-2
50-3
51
50N-1
50N-2
50N-3
51N
2.2.2
Definite Time High-set Elements 50-3, 50-2, 50N-3, 50N-2
For each Element an individual pickup value 50-3 PICKUP, 50-2 PICKUP or 50N-3 PICKUP, 50N-2
PICKUP is set. For 50-3 PICKUP and 50N-3 PICKUP, apart from Fundamental and True RMS, the
Instantaneous values can also be measured. Each phase and ground current is compared separately per
Element with the common pickup values 50-3 PICKUP, 50-2 PICKUP or 50N-3 PICKUP, 50N-2 PICKUP.
If the respective pickup value is exceeded, this is signaled. After the user-defined time delays 50-3 DELAY,
50-2 DELAY or 50N-3 DELAY, 50N-2 DELAY have elapsed, trip signals are issued which are available for
each Element. The dropout value is roughly equal to 95% of the pickup value for currents > 0.3 I
surement of the instantaneous values has been configured for the 50-3 or 50N-3 Element, the dropout ratio
amounts to 90 %.
Pickup can be stabilized by setting dropout times 1215 50 T DROP-OUT or 1315 50N 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. The trip delay time 50-3 DELAY, 50-2 DELAY or 50N-3 DELAY, 50N-2
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 50-3 PICKUP, 50-2 PICKUP or 50N-3 PICKUP,
50N-2 PICKUP has been exceeded again. If the threshold is exceeded again during the dropout delay time,
the time is cancelled. The trip delay time 50-3 DELAY, 50-2 DELAY or 50N-3 DELAY, 50N-2 DELAY con-
tinues running in the meantime. If the threshold value is exceeded and the timedelay expires, the trip command
is issued immediately. If the threshold value is not exceeded at this time, there is no response. If the threshold
value is exceeded again after expiry of the trip-command delay time, while the dropout delay time is still run-
ning, tripping occurs immediately.
The pickup values of each 50-2, 50-3 Element for phase currents and 50N-2, 50N-3 Element for the ground
current and the element-specific time delays can be set individually.
The following figures show the logic diagrams for the 50-2 and 50N-2 high-set elements as an example. They
also apply analogously to the high-set elements 50-3 and 50N-3.
SIPROTEC, 7SK80, Manual
E50417-G1140-C344-A4, Release date 08.2010
Interconnection to other functions
Manual CLOSE
2.2 Overcurrent Protection 50, 51, 50N, 51N
Dynamic cold load pickup
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Inrush restraint
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