Siemens 7SC80 Manual page 191

[stoerfallverlauf-mit-stromkriterium-260602-kn, 1, en_US]
Figure 2-50
Upon the closing of the circuit breaker, current criterion is delayed for a short period of time. If the voltage
criterion drops out during this time period (about 60 ms), the protection function does not pick up. Therefore
no fault record is created when voltage protection is activated in a healthy system. It is important to under-
stand, however, that if a low voltage condition exists on the load after the circuit breaker is closed (unlike
Figure 2-50), the desired pickup of the element will be delayed by 60 ms.
The following figure shows the logic diagram of the undervoltage protection function.
The logic diagram also applies to setting the phase-specific undervoltage protection (Vphph selective or
Vph-n selective). The threshold values and time delays have to be replaced with the phase-specific
values.
SIPROTEC Compact, 7SC80, Manual
E50417-G1140-C486-A8, Edition 07.2017
Typical fault profile for load side connection of the voltage transformers (with current supervi-
sion)
Functions
2.6 Voltage Protection 27, 59
191