ABB RET670 Applications Manual page 42

Section 3
IED application
Setting of current input:
Set parameter
CT_WyePoint with
Transformer as
reference object.
Correct setting is
"ToObject"
ANSI05000461 V1 EN
Figure 4: Example how to set CT_WyePoint parameters in the IED
36
Transformer
Transformer and
Line protection
In this example one IED includes both transformer and line protection 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 a sufficient number of analog current inputs an alternative solution is
shown in figure 5. The same currents are fed to two separate groups of inputs and the
Setting of current input:
Set parameter
CT_WyePoint with
Transformer as
reference object.
Correct setting is
"ToObject"
1MRK504116-UUS C
Line
Forward Reverse
Definition of direction for
directional
line functions
en05000461_ansi.vsd
Application manual