9.4.7.5 Overexcitation alarmA separate step, AlarmPickup, is provided for alarming purpose. It is normally set 2%lower than (Pickup1) and has a definite time delay, tAlarm. This will give the operator anearly warning.9.4.7.6 Logic diagramANSI09000161-5-en.vsd1ANDANDEi M=(Ei / f)(Vn / fn)M = relative Pickup as service valuePick up2M>Pick up2Pick up1M>Pickup1TDForIEEECalc ulationof inte rnalinducedvoltage EiTD MMt>tAlarmt>tMinALARMAlarmPickupV3PBLOCK00-tAlarm00-tMin00-1800s100 msTRIPANSI09000161 V5 ENFigure 141: A simplified logic diagram of the Overexcitation protection OEXPVPH(24)Simplification of the diagram is in the way the IEEE delays are calculated. The coolingprocess is not shown. It is not shown that voltage and frequency are separately checkedagainst their respective limit values.9.4.8 Technical dataTable 177:OEXPVPH (24) technical dataFunction Range or value AccuracyTrip value, pickup (100–180)% of (VBase/fn) ± 0.5% of VTrip value, alarm (50–120)% of pickup level ± 0.5% of Vn at V ≤ Vn± 0.5% of V at V > VnTrip value, high level (100–200)% of (VBase/fn) ± 0.5% of VTable continues on next pageSection 9 1MRK 502 048-UUS AVoltage protection308Technical manual
