10.2.2
Functionality
Overfrequency protection function SAPTOF 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 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 is provided with an 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
10.2.3
Function block
IEC06000280_2_en.vsd
SAPTOF
U3P*
BLOCK
BLKTRIP
TRIP
START
BLKDMAGN
FREQ
IEC06000280 V2 EN
Figure 265:
SAPTOF function block
10.2.4
Signals
Table 309:
SAPTOF Input signals
Name
Type
Default
Description
U3P
GROUP
SIGNAL
-
Three phase group signal for voltage inputs
BLOCK
BOOLEAN
0
Block of function
BLKTRIP
BOOLEAN
0
Blocking operate output
Table 310:
SAPTOF Output signals
Name
Type
Description
TRIP
BOOLEAN
General trip signal
START
BOOLEAN
General start signal
BLKDMAGN
BOOLEAN
Measurement blocked due to low amplitude
FREQ
REAL
Measured frequency
1MRK502052-UEN B
Section 10
Frequency protection
549
Technical manual
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