Example On How To Connect An Open Delta Vt To The Ied For High Impedance Grounded Or Ungrounded Netwoeks - ABB Relion 670 Series Applications Manual

1MRK 511 358-UUS A
3)
4)
5)
4.2.4.5 Example on how to connect an open delta VT to the IED for high impedance
grounded or ungrounded netwoeks
Figure 34
grounded or ungrounded power systems. It shall be noted that this type of VT connection
presents a secondary voltage proportional to 3V0 to the IED.
In case of a solid ground fault close to the VT location the primary value of 3Vo will be equal to:
=
3 Vo 3
EQUATION1922-ANSI V1 EN-US
The primary rated voltage of an open Delta VT is always equal to V
VT secondary windings gives a secondary voltage equal to three times the individual VT secondary
winding rating. Thus the secondary windings of open delta VTs quite often have a secondary rated
voltage equal to one third of the rated phase-to-phase VT secondary voltage (110/3V in this
particular example).
Figure 34
available to the built-in protection and control functions within the IED as well.
Application manual
are three connections made in the Signal Matrix tool (SMT), Application configuration tool (ACT), which
connects 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 than one preprocessing
block might be connected in parallel to these three VT inputs
shows that in this example the fourth (that is, residual) input channel of the preprocessing block is not
connected in SMT. Note. If the parameters V
connected here.
Preprocessing block has a 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:
ConnectionType = Ph-Ph
VBase=13.8 kV
If frequency tracking and compensation is required (this feature is typically required only for IEDs
installed in the generating stations) then the setting parameters
gives an example about the wiring of an open delta VT to the IED for high impedance
× = ×
V 3 V
- -
Ph Ph Ph Gnd
gives overview of required actions by the user in order to make this measurement
, V , V , V should be used the open delta must be
A B C N
DFTReference shall be set accordingly.
Ph-Gnd
Section 4
Analog inputs
SEMOD55055-163 v8
(Equation 3)
. Three series connected
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