4.2.2.3 Example 3
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"
ReverseForward
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
Figure 9: 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
10. 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 direction
Section 4 1MRK 506 369-UUS -
Analog inputs
70 Line distance protection REL670 2.2 ANSI
Application manual
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