Example On How To Connect An Open Delta Vt To The Ied For High Impedance Earthed Or Unearthed Networks - ABB REG670 Applications Manual

Section 4
Analog inputs
4.2.4.5
86
3) 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
4) 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 U
open delta must be connected here.
5) 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
UBase=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
set accordingly.
Example on how to connect an open delta VT to the IED for high
impedance earthed or unearthed networks
Figure 28 gives an example about the wiring of an open delta VT to the IED for high
impedance earthed or unearthed power systems. It shall be noted that this type of VT
connection presents a secondary voltage proportional to 3U0 to the IED.
In case of a solid earth fault close to the VT location the primary value of 3Uo will be
equal to:
= × = ×
3 0 U 3 U 3 U
-
Ph Ph Ph N
EQUATION1921 V3 EN
The primary rated voltage of an open Delta VT is always equal to U
connected 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 28 gives overview of 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.
Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062
-
1MRK 502 071-UEN -
, U , U , U should be used the
L1 L2 L3 N
DFTReference shall be
(Equation 3)
. Three series
Ph-E
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