Siemens SIPROTEC 4 Manual page 134

Functions
2.7 Negative Sequence Protection 46
When the negative sequence protection criteria are no longer satisfied (i.e. all phase currents below 0.1 x Ι
at least one phase current is greater than 10 x Ι
function are reset.
[7sj80-schieflastschutz-20060109, 1, en_US]
Figure 2-50
The pickup of the definite time overcurrent protection can be stabilized by the configured dropout time 4012
46 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 command delay time continues
running. After the dropout delay time has elapsed, the pickup is reported OFF and the trip delay time is reset
unless the threshold has been exceeded again. If the threshold is exceeded again during the dropout delay
time, the time is canceled. The trip command delay time continues running. Should the threshold value be
exceeded after its expiry, the trip command is issued immediately. If the threshold value is not exceeded at
this time, there will be 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 occurs immediately.
The configured dropout times do not influence the tripping times of the inverse time elements as these
depend dynamically on the measured current value. For purposes of dropout coordination, disc emulation is
used with electro-mechanical relays.
134
Logic diagram of the unbalanced load protection
) all pickups issued by the negative sequence protection
Nom
E50417-G1140-C343-A8, Edition 12.2017
or
N
SIPROTEC 4, 7SJ80, Manual