Transformer and
Line protection
Transformer
Line
Setting of current input:
Set parameter
CTStarPoint with
Transformer as
reference object.
Correct setting is
"ToObject"
ReverseForward
Definition of direction
for directional
line functions
Setting of current input:
Set parameter
CTStarPoint with
Transformer as
reference object.
Correct setting is
"ToObject"
IED
IEC05000461 V2 EN-US
Figure 9: Example how to set CTStarPoint parameters in the IED
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
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 for
the current channels to the line protection is set with the line as reference object and the
directional functions of the line protection shall be set to
Forward
to protect the line.
1MRK 511 358-UEN A Section 4
Analog inputs
55
Application manual
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