4.5.3.3 FunctionalityThe residual overvoltage protection ROVPTOV is used in distribution networkswhere the residual overvoltage can reach non-acceptable levels in, for example,high impedance earthing.The function starts when the residual voltage exceeds the set limit. ROVPTOVoperates with the definite time (DT) characteristic.The function contains a blocking functionality. It is possible to block functionoutputs, the definite timer or the function itself, if desired.4.5.3.4 Operation principleThe function can be enabled and disabled with the Operation setting. Thecorresponding parameter values are "On" and "Off".The operation of residual overvoltage protection can be described by using amodule diagram. All the modules in the diagram are explained in the next sections.A070748 V2 ENFigure 255: Functional module diagram. Uo represents the residual voltage.Level detectorThe residual voltage can be selected with the Uo signal Sel setting. The selectableoptions are "Measured Uo" and "Calculated Uo". The residual voltage is comparedto the set Start value. If the value exceeds the set Start value, the level detectorsends an enable signal to the timer.TimerOnce activated, the timer activates the START output. The time characteristic isaccording to DT. When the operation timer has reached the value set by Operatedelay time, the OPERATE output is activated. If the fault disappears before themodule operates, the reset timer is activated. If the reset timer reaches the value setby Reset delay time, the operate timer resets and the START output is deactivated.The timer calculates the start duration value START_DUR, which indicates thepercentage ratio of the start situation and the set operation time. The value isavailable in the monitored data view.Section 4 1YHT530004D05 DProtection functions482 615 seriesTechnical Manual
