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Section 23
Basic IED functions
782
DFTRefGrp(n) will use DFT reference from the selected group block, when own group
is selected, an adaptive DFT reference will be used based on calculated signal
frequency from own group. The setting ExternalDFTRef will use reference based on
what is connected to input DFTSPFC.
The setting ConnectionType: Connection type for that specific instance (n) of the
SMAI (if it is Ph-N or Ph-Ph). Depending on connection type setting the not connected
Ph-N or Ph-Ph outputs will be calculated as long as they are possible to calculate. E.g.
at Ph-Ph connection A, B and C will be calculated for use in symmetrical situations. If
N component should be used respectively the phase component during faults I
must be connected to input 4.
Negation: If the user wants to negate the 3ph signal, it is possible to choose to negate
only the phase signals Negate3Ph, only the neutral signal NegateN or both Negate3Ph
+N. negation means rotation with 180° of the vectors.
GlobalBaseSel: Selects the global base value group used by the function to define
(IBase), (VBase) and (SBase).
MinValFreqMeas: The minimum value of the voltage for which the frequency is
calculated, expressed as percent of VBase (for each instance n).
Settings DFTRefExtOut and DFTReference shall be set to default value
InternalDFTRef if no VT inputs are available.
Even if the user sets the AnalogInputType of a SMAI block to
"Current", the MinValFreqMeas is still visible. However, using the
current channel values as base for frequency measurement is not
recommendable for a number of reasons, not last among them being
the low level of currents that one can have in normal operating
conditions.
Examples of adaptive frequency tracking
Preprocessing block shall only be used to feed functions within the
same execution cycles (e.g. use preprocessing block with cycle 1 to
feed transformer differential protection). The only exceptions are
measurement functions (CVMMXN, CMMXU,VMMXU, etc.) which
shall be fed by preprocessing blocks with cycle 8.
When two or more preprocessing blocks are used to feed one protection
function (e.g. over-power function GOPPDOP), it is of outmost
Generator protection REG670 2.2 ANSI and Injection equipment REX060, REX061, REX062
1MRK 502 071-UUS A
/V
N
N
Application manual
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