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.
20.15.5.1
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
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
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
Figure 514:
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.
1MRK502052-UEN B
Section 20
Basic IED functions
1133
Technical manual
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