4.2.1.4 Operation principleThe function can be enabled and disabled with the Operation setting. Thecorresponding parameter values are "On" and "Off".The operation of (F)EFxPTOC can be described by using a module diagram. All themodules in the diagram are explained in the next sections.A070437 V3 ENFigure 140: Functional module diagramLevel detectorThe operating quantity can be selected with the setting Io signal Sel. The selectableoptions are "Measured Io" and "Calculated Io". The operating quantity is compared tothe set Start value. If the measured value exceeds the set Start value, the level detectorsends an enable-signal to the timer module. If the ENA_MULT input is active, the Startvalue setting is multiplied by the Start value Mult setting.The protection relay does not accept the Start value or Start value Multsetting if the product of these settings exceeds the Start value settingrange.The start value multiplication is normally done when the inrush detection function(INRPHAR) is connected to the ENA_MULT input.TimerOnce activated, the timer activates the START output. Depending on the value of theOperating curve type setting, the time characteristics are according to DT or IDMT.When the operation timer has reached the value of Operate delay time in the DT modeor the maximum value defined by the inverse time curve, the OPERATE output isactivated.When the user-programmable IDMT curve is selected, the operation timecharacteristics are defined by the parameters Curve parameter A, Curve parameter B,Curve parameter C, Curve parameter D and Curve parameter E.If a drop-off situation happens, that is, a fault suddenly disappears before the operatedelay is exceeded, the timer reset state is activated. The functionality of the timer inthe reset state depends on the combination of the Operating curve type, Type of resetcurve and Reset delay time settings. When the DT characteristic is selected, the resetSection 4 1MRS758755 AProtection functions264 REC615 and RER615Technical Manual
