ABB REQ650 Applications Manual page 314

Section 15
Basic IED functions
308
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.
Example of adaptive frequency tracking
Task time group 1
SMAI instance 3 phase group
1
SMAI_20_1:1
SMAI_20_2:1 2
SMAI_20_3:1
3
SMAI_20_4:1 4
5
SMAI_20_5:1
6
SMAI_20_6:1
SMAI_20_7:1 7
SMAI_20_8:1 8
9
SMAI_20_9:1
10
SMAI_20_10:1
SMAI_20_11:1 11
SMAI_20_12:1 12
Task time group 2
SMAI instance 3 phase group
1
SMAI_20_1:2
SMAI_20_2:2
2
SMAI_20_3:2 3
SMAI_20_4:2 4
SMAI_20_5:2 5
SMAI_20_6:2 6
SMAI_20_7:2 7
SMAI_20_8:2 8
SMAI_20_9:2 9
SMAI_20_10:2 10
11
SMAI_20_11:2
SMAI_20_12:2 12
IEC09000029_1_en.vsd
IEC09000029 V1 EN
Figure 119: SMAI instances as organized in different task time groups and the
corresponding parameter numbers
The example shows a situation with adaptive frequency tracking with one reference
selected for all instances. In practice each instance can be adapted to the needs of the
actual application. The adaptive frequency tracking is needed in IEDs that belong to
the protection system of synchronous machines and that are active during run-up and
shout-down of the machine. In other application the usual setting of the parameter
DFTReference of SMAI is InternalDFTRef.
DFTRefGrp7
1MRK 505 291-UEN A
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