Hitachi Relion 650 Series Technical Manual page 403

1MRK 511 557-UEN Rev. A
A few points need to be ensured for SMAI to process the analog signal correctly.
• It is not mandatory to connect all the inputs of SMAI function. However, it is very important that
same set of three phase analog signals should be connected to one SMAI function.
• The sequence of input connected to SMAI function inputs GRPxL1, GRPxL2, GRPxL3 and
GRPxN should normally represent phase L1, phase L2, phase L3 and neutral currents
respectively.
• It is possible to connect analog signals available as Ph-N or Ph-Ph to SMAI. ConnectionType
should be set according to the input connected.
• If the GRPxN input is not connected and all three phase-to-earth inputs are connected, SMAI
calculates the neutral input on its own and it is available at the AI3P and AIN outputs. It is
necessary that the ConnectionType should be set to Ph-N.
• If any two phase-to-earth inputs and neutral currents are connected, SMAI calculates the
remaining third phase-to-neutral input on its own and it is available at the AI3P output. It is
necessary that the ConnectionType should be set to Ph-N.
• If any two phase-to-phase inputs are connected, SMAI calculates the remaining third phase-to-
phase input on its own. It is necessary that the ConnectionType should be set to Ph-Ph.
• All three inputs GRPxLx should be connected to SMAI for calculating sequence components for
ConnectionType set to Ph-N.
• At least two inputs GRPxLx should be connected to SMAI for calculating the positive and
negative sequence component for ConnectionType set to Ph-Ph. Calculation of zero sequence
requires GRPxN input to be connected.
• Negation setting inverts (reverse) the polarity of the analog input signal.
Frequency adaptivity
SMAI function performs DFT calculations for obtaining various electrical parameters. DFT uses some
reference frequency for performing calculations. For most of the cases, these calculations are done
using a fixed DFT reference based on system frequency. However, if the frequency of the network is
expected to vary more than 2 Hz from the nominal frequency, more accurate DFT results can be
obtained if the adaptive DFT is used. This means that the frequency of the network is tracked and the
DFT calculation is adapted according to that.
DFTRefExtOut and DFTReference need to be set appropriately for adaptive DFT calculations.
DFTRefExtOut: Setting valid only for the instance of function block SMAI_80_1. It decides the
reference block for external output SPFCOUT.
DFTReference: Reference DFT for the block. This setting decides DFT reference for DFT
calculations. DFTReference set to InternalDFTRef uses fixed DFT reference based on the set
system frequency. DFTReference set to DFTRefGrpX uses DFT reference from the selected group
block, when own group selected adaptive DFT reference will be used based on the calculated signal
frequency from own group. DFTReference set to External DFT Ref will use reference based on input
signal DFTSPFC.
MinValFreqMeas: The minimum value of the voltage for which the frequency is calculated, expressed
as percent of the voltage in the selected Global Base voltage group (GlobalBaseSel).
Technical Manual
Settings DFTRefExtOut and DFTReference shall be set to default value
InternalDFTRef if no VT inputs are available. However, if it is necessary to use
frequency adaptive DFT (DFTReference set to other than default, referring current
measuring SMAI) when no voltages are available, note that the MinValFreqMeas
setting is still set in reference to UBase (of the selected GBASVAL group). This
means that the minimum level for the current amplitude is based on UBase. For
example, if UBase is 20000, the resulting minimum amplitude for current is 20000 *
10% = 2000.
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Section 14
Basic IED functions
397