Hitachi Relion 670 Series Applications Manual page 57

1MRK506375-UEN Rev. N
CT 600/5A
Star Connected
IEC16000136 V1 EN-US
Figure 14:
Where:
1)
2)
3)
4)
5)
Another alternative is to have the star point of the two-phase CT set as shown in Figure 15:
Railway application RER670
Application manual
L1 L2
Protected Object
Star connected two-phase CT set with star point towards the protected object
Shows how to connect two individual phase currents from a star connected two-phase CT set to the two CT
inputs of the IED.
The current inputs are located in the TRM. It shall be noted that for all these current inputs the following
setting values shall be entered for the example shown in Figure 14.
• CTprim=600A
• CTsec=5A
• CTStarPoint=ToObject
Ratio of the first two parameters is only used inside the IED. The third parameter (CTStarPoint=ToObject)
as set in this example causes no change on the measured currents. In other words, currents are already
measured towards the protected object.
These two connections are the links between the two phase current inputs and the two input channels of
the preprocessing function block 4).
The preprocessing block that has the task to digitally filter the connected analog inputs and calculate:
• fundamental frequency phasors for the two input channels
• harmonic content for the two input channels
• positive and zero sequence quantities by using the fundamental frequency phasors for the first two
input channels (channel one taken as reference for sequence quantities)
These calculated values are then available for all built-in protection and control functions within the IED,
which are connected to this preprocessing function block. For this application most of the preprocessing
settings can be left to the default values.
AI2P in the SMAI function block is a grouped signal which contains all the data about the phases L1, L2,
L1–L2, and neutral quantity; in particular the data about fundamental frequency phasors, harmonic content,
positive sequence and zero sequence quantities are available.
AI1, AI2, AI3, AI4 are the output signals from the SMAI function block which contain the fundamental
frequency phasors and the harmonic content of the corresponding input channels of the preprocessing
function block.
AIN is the signal which contains the fundamental frequency phasors and the harmonic content of the neutral
quantity. In this example, GRP2N is not connected so this data is calculated by the preprocessing function
block on the basis of the inputs GRPL1 and GRPL2. If GRP2N is connected, the data reflects the measured
value of GRP2N.
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IED
1
2
3
IL1
IL2
IN
4
SMAI2
BLOCK AI2P
^GRP2L1 AI1
5
^GRP2L2 AI2
^GRP2L1L2 AI3
^GRP2N
AI4
AIN
IEC16000136-1-en.vsdx
Section 4
Analog inputs
51