ABB Relion 670 Series Applications Manual page 475

1MRK 505 370-UUS Rev. K
20.11.2 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
TRM_40.CH7(U)
ANSI10000060 V1 EN-US
Figure 235: Connection example
20.11.3 SMAI incorrect calculated phase-earth
In some configurations SMAI may produce incorrectly calculated phase-earth values, when this is the
case, a hint will be available in LHMI with text as below.
Calculated phase-earth values are used from one or more SMAIs configured for phase-phase inputs,
without connection to N input.
Busbar protection REB670
Application manual
235 to make SMAI calculate a positive sequence voltage.
SMAI1
SPFCOUT
BLOCK
DFTSPFC G1AI3P
VAB
REVROT
PHASEA
^GRP1_A
PHASEB
^GRP1_B
PHASEC
^GRP1_C
NEUTRAL
^GRP1_N
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.
The outputs from the above configured SMAI block shall only be used for Overfrequency
protection (SAPTOF, 81), Underfrequency protection (SAPTUF, 81) and Rate-of-change
frequency protection (SAPFRC, 81) due to that all other information except frequency
and positive sequence voltage might be wrongly calculated.
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SAPTOF
V3P*
BLOCK
G1AI1
BLKTRIP BLKDMAGN
G1AI2
G1AI4
G1N
GUID-B494B93C-B5AA-4FD6-8080-8611C34C2AD8 v5
TRIP SAPTOF(1)_TRIP
PICK UP
FREQ
ANSI10000060-1-en.vsdx
GUID-7AE6FC17-74AA-403B-8559-3B9D6DA1E433 v1
Section 20
Basic IED functions
469