9.2.5 SettingsTable 163:SAPTOF Group settings (basic)Name Values (Range) Unit Step Default DescriptionOperation OffOn- - Off Operation Off / OnStartFrequency 35.00 - 75.00 Hz 0.01 51.20 Frequency set valuetDelay 0.000 - 60.000 s 0.001 0.200 Operate time delay9.2.6 Monitored dataTable 164:SAPTOF Monitored dataName Type Values (Range) Unit DescriptionFREQ REAL - Hz Measured frequency9.2.7 Operation principleOverfrequency protection SAPTOF is used to detect high power system frequency.SAPTOF has a settable definite time delay. If the frequency remains above the setvalue for a time period corresponding to the chosen time delay, the correspondingTRIP signal is issued. To avoid an unwanted TRIP due to uncertain frequencymeasurement at low voltage magnitude, a voltage controlled blocking of thefunction is available from the preprocessing function, that is, if the voltage is lowerthan the set blocking voltage in the preprocessing function, the function is blockedand no START or TRIP signal is issued.9.2.7.1 Measurement principleThe fundamental frequency of the positive sequence voltage is measuredcontinuously, and compared with the set value, StartFrequency. Over frequencyprotection SAPTOF is dependent on the voltage magnitude. If the voltagemagnitude decreases below the setting MinValFreqMeas in the SMAIpreprocessing function, which is set as a percentage of a global base voltageparameter UBase, SAPTOF is blocked, and the output BLKDMAGN is issued. Allvoltage settings are made in percent of the global parameter UBase. To avoidoscillations of the output START signal, a hysteresis has been included.9.2.7.2 Time delayThe time delay for SAPTOF is a settable definite time delay, specified by thesetting tDelay.TRIP signal issuing requires that the over frequency condition continues for at leastthe user set time delay. If the START condition, with respect to the measuredSection 9 1MRK 502 034-UEN -Frequency protection260Technical Manual
