Section 10
Frequency protection
10.1
Underfrequency protection SAPTUF
10.1.1
Identification
Function description
IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Underfrequency protection
SAPTUF
f <
SYMBOL-P V1 EN
81
10.1.2
Functionality
Underfrequency occurs as a result of a lack of generation in the network.
Underfrequency protection SAPTUF measures frequency with high accuracy, and is
used for load shedding systems, remedial action schemes, gas turbine startup and so
on. Separate definite time delays are provided for operate and restore.
SAPTUF is provided with undervoltage blocking.
The operation is based on positive sequence voltage measurement and requires two
phase-phase or three phase-neutral voltages to be connected. For information about
how to connect analog inputs, refer to
Application manual/IED application/Analog
inputs/Setting guidelines
10.1.3
Function block
IEC06000279_2_en.vsd
SAPTUF
U3P*
BLOCK
BLKTRIP
BLKREST
TRIP
START
RESTORE
BLKDMAGN
FREQ
IEC06000279 V2 EN
Figure 262:
SAPTUF function block
1MRK502052-UEN B
Section 10
Frequency protection
543
Technical manual
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