3)
are three connections made in Signal Matrix Tool (SMT), which connect these three
voltage inputs to first three input channels of the preprocessing function block 5).
Depending on the type of functions which need this voltage information, more then one
preprocessing block might be connected in parallel to these three VT inputs.
4)
shows that in this example the fourth (that is, residual) input channel of the
preprocessing block is not connected in SMT tool. Thus the preprocessing block will
automatically calculate 3Uo inside by vectorial sum from the three phase to earth
voltages connected to the first three input channels of the same preprocessing block.
Alternatively, the fourth input channel can be connected to open delta VT input, as
.
5)
is a Preprocessing block that has the task to digitally filter the connected analog inputs
and calculate:
•
fundamental frequency phasors for all input channels
•
harmonic content for all input channels
•
positive, negative and zero sequence quantities by using the fundamental
frequency phasors for the first three input channels (channel one taken as
reference for sequence quantities)
These calculated values are then available for all built-in protection and control
functions within the IED, which are connected to this preprocessing function block in the
configuration tool. For this application most of the preprocessing settings can be left to
the default values. However the following settings shall be set as shown here:
UBase=66 kV (that is, rated Ph-Ph voltage)
If frequency tracking and compensation is required (this feature is typically required
only for IEDs installed in the generating stations) then the setting parameters
DFTReference shall be set accordingly.
4.2.4.4
Example on how to connect a phase-to-phase connected VT to the
IED
SEMOD55055-134 v7
Figure
gives an example how to connect a phase-to-phase connected VT to the
IED. It gives an overview of the required actions by the user in order to make this
measurement available to the built-in protection and control functions within the
IED. It shall be noted that this VT connection is only used on lower voltage levels
(that is, rated primary voltage below 40 kV).
1MRK 511 407-UEN C
Section 4
Analog inputs
Phasor measurement unit RES670 2.2 IEC
69
Application manual
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