TimeUNormal voltageU1<U2<IntBlkStVal1IntBlkStVal2DisconnectiontBlkUV1 <t1,t1MintBlkUV2 <t2,t2MinBlock step 1Block step 2en05000466.vsdIEC05000466 V1 ENFigure 232: Blocking function9.1.7.4 DesignThe voltage measuring elements continuously measure the three phase-to-neutralvoltages or the three phase-to-phase voltages. Recursive fourier filters or true RMSfilters of input voltage signals are used. The voltages are individually compared to theset value, and the lowest voltage is used for the inverse time characteristic integration.A special logic is included to achieve the 1 out of 3, 2 out of 3 and 3 out of 3 criteriato fulfill the START condition. The design of Two step undervoltage protectionUV2PTUV is schematically shown in Figure 233.1MRK502052-UEN B Section 9Voltage protection489Technical manual
