4.4.1.4 Operation principleThe function can be enabled and disabled with the Operation setting. Thecorresponding parameter values are "On" and "Off".The operation of PHPTOV can be described using a module diagram. All the modulesin the diagram are explained in the next sections.PhaseselectionlogicBLOCKOPERATESTARTLeveldetector tTimertU_A_ABU_B_BCU_C_CABlockinglogicGUID-D71B1772-3503-4150-B3FE-6FFD92DE5DB7 V2 ENFigure 211: Functional module diagramLevel detectorThe fundamental frequency component of the measured three-phase voltages arecompared phase-wise to the set value of the Start value setting. If the measured valueis higher than the set value of the Start value setting, the level detector enables thephase selection logic module. The Relative hysteresis setting can be used forpreventing unnecessary oscillations if the input signal slightly differs from the Startvalue setting. After leaving the hysteresis area, the start condition has to be fulfilledagain and it is not sufficient for the signal to only return to the hysteresis area.The Voltage selection setting is used for selecting phase-to-earth or phase-to-phasevoltages for protection.For the voltage IDMT operation mode, the used IDMT curve equations containdiscontinuity characteristics. The Curve Sat relative setting is used for preventingundesired operation.For a more detailed description of the IDMT curves and the use of theCurve Sat Relative setting, see the IDMT curve saturation of the overvoltage protection section in this manual.Phase selection logicIf the fault criteria are fulfilled in the level detector, the phase selection logic detectsthe phase or phases in which the fault level is detected. If the number of faulty phasesmatch with the set Num of start phases, the phase selection logic activates the Timer.1MRS758755 A Section 4Protection functionsREC615 and RER615 407Technical Manual
