ABB Relion REC670 - Example on How to Connect a Phase-To-Phase Connected VT to the IED

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 shown in figure 22.
5) is a Preprocessing block that has the task to digitally filter the connected analog inputs and
calculate:
• fundamental frequency phasors for all four input channels
• harmonic content for all four 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 v6
Figure 21 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 as well. It shall be noted that this
VT connection is only used on lower voltage levels (that is, rated primary voltage below 40 kV).
1MRK 511 358-UEN A Section 4
Analog inputs
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Application manual