ABB RET670 Applications Manual page 50

Section 3
IED application
A B
CT 800/1
Wye Connected
Protected Object
ANSI06000644 V2 EN
Figure 10: Wye connected three-phase CT set with its star point away from the protected object and the residual/
neutral current connected to the IED
44
C
IN
IC
IB
IA
Where:
1) The drawing shows how to connect three individual phase currents from a wye 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 inputs
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
Inside the IED only the ratio of the first two parameters is used. The third parameter as set in
this example will have no influence on the measured currents (that is, currents are already
measured towards the protected object).
4) are three connections made in the Signal Matrix tool (SMT), Application configuration tool
(ACT), which connects these three current inputs to the first three input channels on the
preprocessing function block 6). Depending on the type of functions, which need this current
information, more than one preprocessing block might be connected in parallel to these three
CT inputs.
Table continues on next page
IED
3
1
1
2 AI 01 (I)
3
AI 02 (I)
4
5
AI 03 (I)
6
7
AI 04 (I)
8
9
AI 05 (I)
2 10
11
AI 06 (I)
12
1MRK504116-UUS C
6
4
SMAI2
BLOCK
^GRP2_A
^GRP2_B
^GRP2_C
^GRP2N
TYPE
5
ANSI06000644-2-en.vsd
Application manual
AI3P
AI1
AI2
AI3
AI4
AIN