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.
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 VBase (of the selected GBASVAL group). This means that the
minimum level for the current amplitude is based on VBase. For
example, if VBase is 20000, the resulting minimum amplitude for
current is 20000 * 10% = 2000.
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 (GBASVAL:n, where 1<n<6).
Below example shows a situation with adaptive frequency tracking with one reference
selected for all instances. In practice each instance can be adapted to the needs of the
actual application.
1MRK 505 277-UUS C Section 15
Basic IED functions
405
Technical Manual
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