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 6: Example how to set CTStarPoint 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
7. 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 505 393-UEN B Section 4
Analog inputs
Line differential protection RED650 2.2 IEC 43
Application manual
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