ABB Relion 670 Series Applications Manual page 82

Section 4
Analog inputs
A B
CT 800/1
Star Connected
Protected Object
ANSI11000026 V4 EN-US
Figure 26: Wye connected three-phase CT set with its star point away from the protected object
In the example in
example
current inputs on the TRM (item 2 in the figure):
• CTprim =600A
CTsec =5A
•
CTWyePoint =FromObject
•
Inside the IED only the ratio of the first two parameters is used. 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 the figure below.
76
C
IC
IB
IA
figure 26 case everything is done in a similar way as in the above described
(figure 25). The only difference is the setting of the parameter
IED
2
3
1
1MRK 511 358-UUS A
4
SMAI_20_2
BLOCK AI3P
REVROT AI1
5
^GRP2L1 AI2
^GRP2L2 AI3
^GRP2L3 AI4
^GRP2N AIN
ANSI11000026-4-en.vsd
CTStarPoint of the used
Application manual