ABB Relion Technical Manual page 699

1MRK 502 048-UUS A
Technical manual
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.
Section 17
Basic IED functions
693