4.4.5.2 Function blockGUID-24EBDE8B-E1FE-47B0-878B-EBEC13A27CAC V1 ENFigure 220: Function block4.4.5.3 FunctionalityThe positive-sequence undervoltage protection function PSPTUV is used to detectpositive-sequence undervoltage conditions. PSPTUV is used for the protection ofsmall power generation plants. The function helps in isolating an embedded plantfrom a fault line when the fault current fed by the plant is too low to start an overcurrentfunction but high enough to maintain the arc. Fast isolation of all the fault currentsources is necessary for a successful autoreclosure from the network-end circuitbreaker.The function starts when the positive-sequence voltage drops below the set limit.PSPTUV operates with the definite time (DT) characteristics.The function contains a blocking functionality. It is possible to block function outputs,the definite timer or the function itself, if desired.4.4.5.4 Operation principleThe function can be enabled and disabled with the Operation setting. Thecorresponding parameter values are "On" and "Off".The operation of PSPTUV can be described using a module diagram. All the modulesin the diagram are explained in the next sections.GUID-F1E58B1E-03CB-4A3C-BD1B-F809420397ED V1 ENFigure 221: Functional module diagram. U1 is used for representing positivephase sequence voltage.Level detectorThe calculated positive-sequence voltage is compared to the set Start value setting. Ifthe value drops below the set Start value, the level detector enables the timer. TheRelative hysteresis setting can be used for preventing unnecessary oscillations if the1MRS758755 A Section 4Protection functionsREC615 and RER615 431Technical Manual
