maintained. These time settings are system dependent; higher or lower settings may be required depending on the
particular application.
It is possible to set up r
estoration schemes involving multiple frequencies. This allows faster restoration of loads,
but there is the possibility of continuous system operation at frequencies far removed from the nominal. A typical
scheme using two frequencies is illustrated below:
Stage
Restore Freq. Restoration Frequency
Setting (Hz)
Restore DelayRestoration Time Delay
(S)
Holding Time Delay (S)
1 49.5 Hz 120 sec 20 sec
2 49.5 Hz 60 sec 20 sec
3 49.0 Hz 120 sec 20 sec
4 49.0 Hz 60 sec 20 sec
Staggered time settings may be used in this scheme as well, but the time separation among the restoration of
stages will be a function of the fr
equency recovery pattern. Time coordinated restoration can only be guaranteed
for those stages with a common restoration frequency setting.
P14x Chapter 11 - Frequency Protection Functions
P14xEd1-TM-EN-1 255
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