ABB RELION 670 SERIES REG670 - Example How to Connect the Open Delta VT to the IED for Low Impedance Grounded or Solidly Grounded Power Systems

4.2.4.6 Example how to connect the open delta VT to the IED for low
impedance grounded
or solidly grounded power systems
SEMOD55055-199 v6
Figure
29 gives an example about the connection of an open delta VT to the IED for
low impedance grounded or solidly grounded power systems. It shall be noted that this
type of VT connection presents secondary voltage proportional to
3V
0
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
3
Ph Ph
Ph Gnd
V
Vo V
-
-
= =
EQUATION1927-ANSI V1 EN-US (Equation 7)
The primary rated voltage of such VT is always equal to VPh-Gnd. 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, 1
15V or 115/√3V as in this particular example. Figure
29 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.
1MRK 502 071-UUS A Section 4
Analog inputs
Generator protection REG670 2.2 ANSI and Injection equipment REX060, REX061, REX062 93
Application manual