I
Sec
I
P
r
i
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
Figure 38: Commonly used markings of CT terminals
Where:
a) is symbol and terminal marking used in this document. Terminals marked with a dot 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.
4.2.3.4 Example on how to connect a wye connected three-phase CT set to the
IED
Figure
39 gives an example about the wiring of a wye connected three-phase CT set to the
IED. It gives also an overview of the actions which are needed to make this measurement
available to the built-in protection and control functions within the IED as well.
1MRK 506 334-UUS A Section 4
Analog inputs
95
Application manual
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