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 11: 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!
It shall be noted that depending on national standard and utility practices, the rated
secondary current of a CT has typically one of the following values:
•
1A
•
5A
However, in some cases, the following rated secondary currents are used as well:
• 2A
• 10A
The IED fully supports all of these rated secondary values.
It is recommended to:
•
use 1A rated CT input into the IED in order to connect CT
s
with 1A and 2A secondary rating
• use 5A rated CT input into the IED in order to connect CTs
with 5A and 10A secondary rating
1MRK 506 375-UEN A Section 4
Analog inputs
Railway application RER670 2.2 IEC 49
Application manual
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