ABB RELION RET670 Applications Manual page 978

Section 24
Basic IED functions
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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
importance that parameter setting DFTReference has the same set value
for all of the preprocessing blocks involved
1MRK 504 163-UUS A
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Transformer protection RET670 2.2 ANSI
Application manual
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