Siemens SIPROTEC 7SJ61 Manual page 78

Functions
2.3 Dynamic Cold Load Pickup
If overcurrent elements are picked up while time Active Time is running, the fault generally prevails until
pickup drops out, using the dynamic settings. Only then the parameters are set back to "normal".
If the dynamic setting values were activated via the binary input „>ACTIVATE CLP" or the signal "79M Auto
Reclosing ready" and this cause drops out, the "normal" settings are restored immediately, even if a pickup is
the result.
If the binary input „>BLOCK CLP" is enabled, all triggered timers are reset and, as a consequence, all "normal"
settings are immediately restored. If blocking occurs during an on-going fault with dynamic cold load pickup
functions enabled, the timers of all non-directional overcurrent relay elements are stopped and may then be
restarted based on their normal duration.
During power up of the protective relay with an open circuit breaker, the time delay CB Open Time is started,
and is processed using the "normal" settings. Therefore, when the circuit breaker is closed, the "normal" set-
tings are effective.
Figure 2-17 illustrates the timing sequence. Figure 2-18 shows the logic diagram of the dynamic cold load
pickup feature.
Figure 2-17 Timing charts of the dynamic cold load pickup function
78
SIPROTEC, 7SJ61, Manual
C53000-G1140-C210-1, Release date 02.2008