Example How To Connect The Open Delta Vt To The Ied For Low Impedance Earthed Or Solidly Earthed Power Systems - ABB REG670 Applications Manual

1MRK 502 071-UEN -
4.2.4.6
138
138 kV
3
115 V
3
138 kV
3
115 V
3
IEC06000602 V4 EN
Figure 29: Open delta connected VT in low impedance or solidly earthed power system
Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062
Application manual
Example how to connect the open delta VT to the IED for low
impedance earthed or solidly earthed power systems
Figure 29 gives an example about the connection of an open delta VT to the IED for
low impedance earthed or solidly earthed power systems. It shall be noted that this
type of VT connection presents secondary voltage proportional to 3U
In case of a solid earth fault close to the VT location the primary value of 3Uo will be
equal to:
U
= - =
3 Uo Ph Ph U
-
Ph E
3
EQUATION1926 V1 EN
The primary rated voltage of such VT is always equal to UPh-E Therefore, three series
connected VT secondary windings will give the secondary voltage equal only to one
individual VT secondary winding rating. Thus the secondary windings of such open
delta VTs quite often has a secondary rated voltage close to rated phase-to-phase VT
secondary voltage, that is, 115V or 115/√3V as in this particular example. Figure
gives an overview of the actions which are needed to make this measurement available
to the built-in protection and control functions within the IED.
L1
L2
L3
kV
3
115 V
3
IED
2
3
1
+3Uo
Analog inputs
5
SMAI2
BLOCK
REVROT
# Not Used
^GRP2L1
# Not Used
^GRP2L2
# Not Used ^GRP2L3
^GRP2N
4
IEC06000602-4-en.vsdx
Section 4
to the IED.
0
(Equation 7)
29
AI3P
AI1
AI2
AI3
AI4
AIN
89