•
CTprim
=600A
•
CTsec
=5A
•
CTStarPoint
=FromObject
The ratio of the first two parameters is only used inside the IED. The third parameter as set in
this example will negate the measured currents in order to ensure that the currents are
measured towards the protected object within the IED.
A third alternative is to have the residual/neutral current from the three-phase CT set
connected to the IED as shown in Figure 21.
L1
IL1
IL2
IL3
L2 L3
Protected Object
CT 800/1
Star Connected
IL1
IL2
IL3
IN
IED
1
3
4
2
5
IEC06000644-4-en.vsdx
6
SMAI2
BLOCK
REVROT
^GRP2L1
^GRP2L2
^GRP2L3
^GRP2N
AI3P
AI1
AI2
AI3
AI4
AIN
IEC06000644 V4 EN-US
Figure 22: Star connected three-phase CT set with its star point away from the protected object and
the residual/neutral current connected to the IED
Where:
1) Shows how to connect three individual phase currents from a star connected three-phase CT set to
the three CT inputs of the IED.
2) Shows how to connect residual/neutral current from the three-phase CT set to the fourth input in
the IED. It shall be noted that if this connection is not made, the IED will still calculate this current
internally by vectorial summation of the three individual phase currents.
3) Is the TRM where these current inputs are located. It shall be noted that for all these current inputs
the following setting values shall be entered.
•
CTprim
=800A
•
CTsec
=1A
•
CTStarPoint
=FromObject
•
ConnectionType
=Ph-N
The ratio of the first two parameters is only used inside the IED. The third parameter as set in this
example will have no influence on measured currents (that is, currents are already measured
towards the protected object).
Table continues on next page
1MRK 505 370-UEN D Section 4
Analog inputs
Busbar protection REB670 69
Application manual
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