8.10.6 Monitored dataTable 152:VRPVOC Monitored dataName Type Values (Range) Unit DescriptionIMAX REAL - A Maximum phase currentmagnitudeUUMIN REAL - kV Minimum ph-to-phvoltage magnitude8.10.7 Operation principle8.10.7.1 Measured quantitiesThe voltage-restrained time overcurrent protection VRPVOC function is alwaysconnected to three-phase current and three-phase voltage input in the configurationtool (ACT), but it will always measure the maximum of the three-phase currents andthe minimum of the three phase-to-phase voltages.8.10.7.2 Base quantitiesGlobalBaseSel: Selects the global base value group used by the function to define(IBase), (UBase) and (SBase).IBase shall be entered as rated phase current of the protected object in primaryamperes.UBase shall be entered as rated phase-to-phase voltage of the protected object inprimary kV.8.10.7.3 Overcurrent protectionThe overcurrent step simply compares the magnitude of the measured current quantitywith the set start level. The overcurrent step starts if the magnitude of the measuredcurrent quantity is bigger than the set level.Voltage restraint/control featureThe overcurrent protection operation is made dependent of a measured voltagequantity. This means that the start level of the overcurrent step is not constant butdecreases with the decrease in the magnitude of the measured voltage quantity. Twodifferent types of dependencies are available:• Voltage restraint overcurrent (when setting parameter VDepMode = Slope)Section 8 1MRK 502 048-UEN ACurrent protection252Technical manual
