Note that all other functions, with a few exceptions, use this output in
configuration. Note that the SMAI function will always calculate the residual sum
of current/voltage if the input GRPxN is not connected in SMT. Applications with
a few exceptions shall always be connected to AI3P.
21.8.5.1 Frequency values
GUID-B494B93C-B5AA-4FD6-8080-8611C34C2AD8 v5
The SMAI function includes a functionality based on the level of positive sequence
voltage, MinValFreqMeas, to validate if the frequency measurement is valid or not.
If the positive sequence voltage is lower than MinValFreqMeas, the function
freezes the frequency output value for 500 ms and after that the frequency output is
set to the nominal value. A signal is available for the SMAI function to prevent
operation due to non-valid frequency values. MinValFreqMeas is set as % of
UBase/√3
If SMAI setting ConnectionType is Ph-Ph, at least two of the inputs GRPxL1,
GRPxL2 and GRPxL3, where 1≤x≤12, must be connected in order to calculate the
positive sequence voltage. Note that phase to phase inputs shall always be
connected as follows: L1-L2 to GRPxL1, L2-L3 to GRPxL2, L3-L1 to GRPxL3. If
SMAI setting ConnectionType is Ph-N, all three inputs GRPxL1, GRPxL2 and
GRPxL3 must be connected in order to calculate the positive sequence voltage.
If only one phase-phase voltage is available and SMAI setting ConnectionType is
Ph-Ph, the user is advised to connect two (not three) of the inputs GRPxL1,
GRPxL2 and GRPxL3 to the same voltage input as shown in figure
371 to make
SMAI calculate a positive sequence voltage.
SMAI1
BLOCK
DFTSPFC
REVROT
^GRP1L1
^GRP1L2
^GRP1L3
^GRP1N
SPFCOUT
G1AI3P
G1AI1
G1AI2
G1AI4
G1N
NEUTRAL
PHASEL3
PHASEL2
PHASEL1
UL1L2
SAPTOF
U3P*
BLOCK
BLKTRIP
TRIP
START
BLKDMAGN
FREQ
TRM _40.CH7(U)
SAPTOF(1)_TRIP
EC10000060-3-en.vsdx
IEC10000060 V3 EN-US
Figure 371: Connection example
The above described scenario does not work if SMAI setting
ConnectionType is Ph-N. If only one phase-earth voltage is
available, the same type of connection can be used but the SMAI
ConnectionType setting must still be Ph-Ph and this has to be
accounted for when setting MinValFreqMeas. If SMAI setting
ConnectionType is Ph-N and the same voltage is connected to all
three SMAI inputs, the positive sequence voltage will be zero and
the frequency functions will not work properly.
1MRK 505 394-UEN A Section 21
Basic IED functions
Line differential protection RED650 2.2 IEC 803
Technical manual
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