ABB RELION RET670, Applications Manual

Page: 78 / 1016

4.2.2.3 Example 3
SEMOD55055-35 v7
One IED used to protect two objects.
Transformer and
Line protection
Transformer
Line
Setting of current input:
Set parameter
CT_WyePoint with
Transformer as
reference object.
Correct setting is
"ToObject"
Reverse Forward
Definition of direction for
directional
line functions
Setting of current input:
Set parameter
CT_WyePoint with
Transformer as
reference object.
Correct setting is
"ToObject"
en05000461_ansi.vsd
ANSI05000461 V1 EN-US
Figure 10: Example how to set CT_WyePoint parameters in the IED
In this example, one IED includes both transformer and line protections and the line
protection uses the same CT as the transformer protection does. For both current input
channels, the CT direction is set with the transformer as reference object. This means
that the direction
Forward for the line protection is towards the transformer. To look
towards the line, the direction of the directional functions of the line protection must be
set to
Reverse . The direction Forward / Reverse is related to the reference object that is
the transformer in this case.
When a function is set to Reverse and shall protect an object in reverse direction, it
shall be noted that some directional functions are not symmetrical regarding the reach
in forward and reverse direction. It is in first hand the reach of the directional criteria
that can differ. Normally it is not any limitation but it is advisable to have it in mind
and check if it is acceptable for the application in question.
If the IED has sufficient number of analog current inputs, an alternative solution is
shown in Figure
11 . The same currents are fed to two separate groups of inputs and the
line and transformer protection functions are configured to the different inputs. The CT
Section 4
1MRK 504 163-UUS A
Analog inputs
72 Transformer protection RET670 2.2 ANSI
Application manual