Table 160: SAPTOF Output signals
Name Type Description
TRIP BOOLEAN General trip signal
START BOOLEAN General start signal
BLKDMAGN BOOLEAN Measurement blocked due to low amplitude
10.2.5 Settings
Table 161: SAPTOF Group settings (basic)
Name Values (Range) Unit Step Default Description
Operation Off
On
- - Off Operation Off / On
StartFrequency 35.00 - 75.00 Hz 0.01 51.20 Frequency set value
tDelay 0.000 - 60.000 s 0.001 0.200 Operate time delay
10.2.6 Monitored data
Table 162: SAPTOF Monitored data
Name
Type Values (Range) Unit Description
FREQ REAL - Hz Measured frequency
10.2.7 Operation principle
Overfrequency protection SAPTOF is used to detect high power system frequency.
SAPTOF has a settable definite time delay. If the frequency remains above the set
value for a time period greater than the set time delay the TRIP signal is issued. To
avoid an unwanted TRIP due to uncertain frequency measurement at low voltage
magnitude, a voltage controlled blocking of the function is available from the
preprocessing function, that is, if the voltage is lower than the set blocking voltage in
the preprocessing function, the function is blocked and no START or TRIP signal is
issued.
10.2.7.1 Measurement principle
The frequency measuring element continuously measures the frequency of the
positive sequence voltage and compares it to the setting StartFrequency. The
frequency signal is filtered to avoid transients due to switchings and faults in the
power system. If the voltage magnitude decreases below the setting MinValFreqMeas
in the SMAI preprocessing function, which is discussed in the Basic IED Functions
chapter and is set as a percentage of a global base voltage parameter UBase, SAPTOF
is blocked and the output BLKDMAGN is issued. All voltage settings are made in
Section 10 1MRK 504 135-UEN A
Frequency protection
236
Technical manual
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