8.1.2.2 Disconnected equipment detectionThe setting must be below the lowest occurring "normal" voltage and above the highestoccurring voltage, caused by inductive or capacitive coupling, when the equipment isdisconnected.8.1.2.3 Power supply qualityThe setting must be below the lowest occurring "normal" voltage and above the lowestacceptable voltage, due to regulation, good practice or other agreements.8.1.2.4 Voltage instability mitigationThis setting is very much dependent on the power system characteristics, and thoroughstudies have to be made to find the suitable levels.8.1.2.5 Backup protection for power system faultsThe setting must be below the lowest occurring "normal" voltage and above the highestoccurring voltage during the fault conditions under consideration.8.1.2.6 Settings for Two step undervoltage protectionThe following settings can be done for Two step undervoltage protection UV2PTUV(27):ConnType: Sets whether the measurement shall be phase-to-ground fundamental value,phase-to-phase fundamental value, phase-to-ground RMS value or phase-to-phase RMSvalue.Operation: Disabled or Enabled.VBase (given in GlobalBaseSel): Base voltage phase-to-phase in primary kV. Thisvoltage is used as reference for voltage setting. UV2PTUV (27) measures selectivelyphase-to-ground voltages, or phase-to-phase voltage chosen by the setting ConnType. Thefunction will operate if the voltage gets lower than the set percentage of VBase. WhenConnType is set to PhN DFT or PhN RMS then the IED automatically divides set value forVBase by √3. VBase is used when ConnType is set to PhPh DFT or PhPh RMS. Therefore,always set VBase as rated primary phase-to-phase voltage of the protected object. Thismeans operation for phase-to-ground voltage under:(%) ( )3< ×V VBase kVEQUATION1711 V1 EN (Equation 72)Section 8 1MRK 505 337-UUS -Voltage protection232Application manual
