Table 157:SAPTUF Output signalsName Type DescriptionTRIP BOOLEAN General trip signalSTART BOOLEAN General start signalRESTORE BOOLEAN Restore signal for load restoring purposesBLKDMAGN BOOLEAN Measurement blocked due to low voltageamplitude9.1.5 SettingsTable 158:SAPTUF Group settings (basic)Name Values (Range) Unit Step Default DescriptionOperation OffOn- - Off Operation Off / OnStartFrequency 35.00 - 75.00 Hz 0.01 48.80 Frequency set valuetDelay 0.000 - 60.000 s 0.001 0.200 Operate time delaytRestore 0.000 - 60.000 s 0.001 0.000 Restore time delayRestoreFreq 45.00 - 65.00 Hz 0.01 49.90 Restore frequency if frequency is abovefrequency value9.1.6 Monitored dataTable 159:SAPTUF Monitored dataName Type Values (Range) Unit DescriptionFREQ REAL - Hz Measured frequency9.1.7 Operation principleUnderfrequency protection (SAPTUF) function is used to detect low power systemfrequency. If the frequency remains below the set value for a time periodcorresponding to the chosen time delay, the corresponding trip signal is issued. Toavoid an unwanted trip due to uncertain frequency measurement at low voltagemagnitude, a voltage controlled blocking of the function is available from thepreprocessing function, that is, if the voltage is lower than the set blocking voltagein the preprocessing function, the function is blocked and no START or TRIPsignal is issued.9.1.7.1 Measurement principleThe fundamental frequency of the measured input voltage is measuredcontinuously, and compared with the set value, StartFrequency. The frequencyfunction is dependent on the voltage magnitude. If the voltage magnitude decreasesthe setting MinValFreqMeas in the SMAI preprocessing function, which is set as aSection 9 1MRK 502 034-UEN -Frequency protection256Technical Manual
