Table 141:SAPTOF Output signalsName Type DescriptionTRIP BOOLEAN General trip signalSTART BOOLEAN General start signalBLKDMAGN BOOLEAN Measurement blocked due to low amplitude8.2.5 SettingsTable 142: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 delay8.2.6 Monitored dataTable 143:SAPTOF Monitored dataName Type Values (Range) Unit DescriptionFREQ REAL - Hz Measured frequency8.2.7 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 greater than the set time delay the 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 voltage inthe preprocessing function, the function is blocked and no START or TRIP signal isissued.8.2.7.1 Measurement principleThe frequency measuring element continuously measures the frequency of thepositive sequence voltage and compares it to the setting StartFrequency. Thefrequency signal is filtered to avoid transients due to switchings and faults in thepower system. If the voltage magnitude decreases below the setting MinValFreqMeasin the SMAI preprocessing function, which is discussed in the Basic IED Functionschapter and is set as a percentage of a global base voltage parameter UBase, SAPTOFis blocked and the output BLKDMAGN is issued. All voltage settings are made inSection 8 1MRK 511 287-UEN AFrequency protection184Technical manual
