Function Range or value Accuracy
Reset time, pickup function At 50 Hz: 60 ms typically at f
set
-0.5 Hz to f
set
+0.5 Hz
At 60 Hz: 50 ms typically at f
set
-0.5 Hz to f
set
+0.5 Hz
-
Operate time delay (0.000-60.000)s <250 ms
Restore time delay (0.000-60.000)s <150 ms
8.2 Overfrequency protection SAPTOF (81)
8.2.1 Identification
Function description IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Overfrequency protection SAPTOF
SYMBOL-O V1 EN
81
8.2.2 Functionality
Overfrequency protection function SAPTOF (81) is applicable in all situations, where
reliable detection of high fundamental power system frequency is needed.
Overfrequency occurs because of sudden load drops or shunt faults in the power network.
Close to the generating plant, generator governor problems can also cause over frequency.
SAPTOF (81) measures frequency with high accuracy, and is used mainly for generation
shedding and remedial action schemes. It is also used as a frequency stage initiating load
restoring. A definite time delay is provided for operate.
SAPTOF (81) is provided with an undervoltage blocking.
1MRK 511 287-UUS A Section 8
Frequency protection
195
Technical manual
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