Siemens 7SC80 Manual page 77

[7sc80-abhueberstromzeit-erde-131106, 1, en_US]
Figure 2-12
If an ANSI characteristic is configured, parameter 1309 51N TIME DIAL is used instead of parameter 1308
51N TIME DIAL.
If parameter 1313 MANUAL CLOSE is set to 51N instant. and manual close detection is used, a pickup
causes instantaneous tripping even if the element is blocked via a binary input.
The same applies to 79 AR 51N inst.
Dropout Behavior
For the ANSI or IEC characteristics, you can select whether an element drops out instantaneously after a
threshold has been undershot or whether dropout is performed by means of disk emulation. "Instantaneous"
means that the picked-up element drops out when 95 % of the pickup value is undershot. For a new pickup,
the time delay starts at zero.
The disk emulation evokes a dropout process (timer counter is decrementing) which begins after de-energiza-
tion. This process corresponds to the reset of a Ferraris disk (explaining its denomination "disk emulation"). In
case several faults occur in succession, the "history" is taken into consideration due to the inertia of the
SIPROTEC Compact, 7SC80, Manual
E50417-G1140-C486-A8, Edition 07.2017
Logic diagram of the inverse time overcurrent protection for ground
2.2 Overcurrent Protection 50, 51, 50N, 51N
Functions
77