Regardless which one of the above two options is selected, busbar differential
protection will behave correctly.
The main CT ratios must also be set. This is done by setting the two parameters CT
sec
and CTprim for each current channel. For a 1000/5 A CT, the following settings shall
be used:
• CTprim = 1000 (value in A)
• CTsec =5 (value in A).
4.2.2.4 Examples on how to connect, configure and set CT inputs for most
commonly used CT connections
SEMOD55055-296 v7
Figure
13 defines the marking of current transformer terminals commonly used around
the world:
In the SMAI function block, you have to set if the SMAI block is
measuring current or voltage. This is done with the parameter:
AnalogInputType: Current/V
oltage. The ConnectionType: phase -phase/
phase-ground and GlobalBaseSel.
I
Sec
I
Pri
S1 (X1)
P1
(H1)
P2
(H2)
S2 (X2)
P2
(H2)
P1
(H1)
x x
a) b) c)
en06000641.vsd
S2 (X2)
S1 (X1)
IEC06000641 V1 EN-US
Figure 13: Commonly used markings of CT terminals
Where:
a) is symbol and terminal marking used in this document. Terminals marked with a square
indicates the primary and secondary winding terminals with the same (that is, positive)
polarity
b) and
c)
are equivalent symbols and terminal marking used by IEC (ANSI) standard for CTs. Note that
for these two cases the CT polarity marking is correct!
1MRK 504 163-UUS A Section 4
Analog inputs
Transformer protection RET670 2.2 ANSI 75
Application manual
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