22.11.2 Frequency values GUID-B494B93C-B5AA-4FD6-8080-8611C34C2AD8 v5The SMAI function includes a functionality based on the level of positive sequencevoltage, MinValFreqMeas, to validate if the frequency measurement is valid or not.If the positive sequence voltage is lower than MinValFreqMeas, the functionfreezes the frequency output value for 500 ms and after that the frequency output isset to the nominal value. A signal is available for the SMAI function to preventoperation due to non-valid frequency values. MinValFreqMeas is set as % ofUBase/√3If SMAI setting ConnectionType is Ph-Ph, at least two of the inputs GRPxL1,GRPxL2 and GRPxL3, where 1≤x≤12, must be connected in order to calculate thepositive sequence voltage. Note that phase to phase inputs shall always beconnected as follows: L1-L2 to GRPxL1, L2-L3 to GRPxL2, L3-L1 to GRPxL3. IfSMAI setting ConnectionType is Ph-N, all three inputs GRPxL1, GRPxL2 andGRPxL3 must be connected in order to calculate the positive sequence voltage.If only one phase-phase voltage is available and SMAI setting ConnectionType isPh-Ph, the user is advised to connect two (not three) of the inputs GRPxL1,GRPxL2 and GRPxL3 to the same voltage input as shown in figure 118 to makeSMAI calculate a positive sequence voltage.SMAI1BLOCKDFTSPFCREVROT^GRP1L1^GRP1L2^GRP1L3^GRP1NSPFCOUTG1AI3PG1AI1G1AI2G1AI4G1NNEUTRALPHASEL3PHASEL2PHASEL1UL1L2SAPTOFU3P*BLOCKBLKTRIPTRIPSTARTBLKDMAGNFREQTRM_40.CH7(U)SAPTOF(1)_TRIPEC10000060-3-en.vsdxIEC10000060 V3 EN-USFigure 118: Connection exampleThe above described scenario does not work if SMAI settingConnectionType is Ph-N. If only one phase-earth voltage isavailable, the same type of connection can be used but the SMAIConnectionType setting must still be Ph-Ph and this has to beaccounted for when setting MinValFreqMeas. If SMAI settingConnectionType is Ph-N and the same voltage is connected to allthree SMAI inputs, the positive sequence voltage will be zero andthe frequency functions will not work properly.The outputs from the above configured SMAI block shall only beused for Overfrequency protection (SAPTOF), Underfrequencyprotection (SAPTUF) and Rate-of-change frequency protectionSection 22 1MRK 511 407-UEN CBasic IED functions342 Phasor measurement unit RES670 2.2 IECApplication manual
