24.11.2 Frequency values
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 VBase/√3
If SMAI setting ConnectionType is Ph-Ph, at least two of the inputs GRPx_A, GRPx_B
and GRPx_C, 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:
A-B to GRPxA, B-C to GRPxB, C-A to GRPxC. If SMAI setting ConnectionType is Ph-
N, all three inputs GRPx_A, GRPx_B and GRPx_C 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 GRPx_A, GRPx_B and
GRPx_C to the same voltage input as shown in figure
415 to make SMAI calculate a
positive sequence voltage.
SMAI1
BLOCK
DFTSPFC
REVROT
^GRP1_A
^GRP1_B
^GRP1_C
^GRP1_N
SPFCOUT
G1AI3P
G1AI1
G1AI2
G1AI4
G1N
NEUTRAL
PHASEC
PHASEB
PHASEA
VAB
SAPTOF
V3P*
BLOCK
BLKTRIP
TRIP
PICK UP
BLKDMAGN
FREQ
TRM_40.CH7(U)
SAPTOF(1)_TRIP
ANSI10000060-1-en.vsdx
ANSI10000060 V1 EN
Figure 415: Connection example
The above described scenario does not work if SMAI setting
ConnectionType is Ph-N. If only one phase-ground 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.
Section 24 1MRK 506 369-UUS -
Basic IED functions
902 Line distance protection REL670 2.2 ANSI
Application manual
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