ABB REB670 Series, Applications Manual

Page: 87 / 476

3
3
Ph Ph
Ph E
U
Uo U
-
-
= =
EQUATION1926 V1 EN-US
(Equation 7)
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 31 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.
1
L1
IED
L2
L3
138
3
115
3
kV
V
+3Uo
138
3
115
3
kV
V
138
3
115
3
kV
V
IEC06000602-4-en.vsdx
# Not Used
# Not Used
# Not Used
SMAI2
BLOCK
REVROT
^GRP2L1
^GRP2L2
^GRP2L3
^GRP2N AI3P
AI1
AI2
AI3
AI4
AI N
2
3
4
5
IEC06000602 V4 EN-US
Figure 31: Open delta connected VT in low impedance or solidly earthed power system
1MRK 505 370-UEN D Section 4
Analog inputs
Busbar protection REB670 81
Application manual