ABB Relion 650 Series Applications Manual page 251

1MRK 505 287-UUS B
16.1.7 Current transformer requirements for CTs according to other
standards
All kinds of conventional magnetic core CTs are possible to use with the IEDs if they fulfill the
requirements corresponding to the above specified expressed as the rated equivalent limiting
secondary e.m.f. E
data for relaying applications it is possible to approximately calculate a secondary e.m.f. of the CT
comparable with E
e.m.f. E
alreq
some other standards are specified below.
16.1.7.1 Current transformers according to IEC 61869-2, class P, PR
A CT according to IEC 61869-2 is specified by the secondary limiting e.m.f. E
is approximately equal to the corresponding E
must have a secondary limiting e.m.f. E
E
2 max
EQUATION1383 V2 EN-US
16.1.7.2 Current transformers according to IEC 61869-2, class PX, PXR (and old IEC
60044-6, class TPS and old British Standard, class X)
CTs according to these classes are specified approximately in the same way by a rated knee point
e.m.f. E
knee
TPS). The value of the E
possible to give a general relation between the E
approximately 80 % of the E
a rated knee point e.m.f. E
= ×
S TD S
EQUATION1893.ANSI V1 EN-US
16.1.7.3 Current transformers according to ANSI/IEEE
Current transformers according to ANSI/IEEE are partly specified in different ways. A rated
secondary terminal voltage V
voltage the CT will deliver to a standard burden at 20 times rated secondary current without
exceeding 10 % ratio correction. There are a number of standardized V
V is 400 V for a C400 CT. A corresponding rated equivalent limiting secondary e.m.f. E
ANSI
be estimated as follows:
Busbar protection REB650
Application manual
according to the IEC 61869-2 standard. From different standards and available
al
. By comparing this with the required rated equivalent limiting secondary
al
it is possible to judge if the CT fulfills the requirements. The requirements according to
>
max E
alreq
(E for class PX and PXR, E
k
is lower than the corresponding E
knee
. Therefore, the CTs according to class PX, PXR, X and TPS must have
al
that fulfills the following:
knee
+ - ×
(1 TD S )
Old Calculated
ANSI
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. Therefore, the CTs according to class P and PR
al
that fulfills the following:
alf
for class X and the limiting secondary voltage V
kneeBS
and the E
knee
is specified for a CT of class C. V
. The value of the E
alf
according to IEC 61869-2. It is not
al
but normally the E
al knee
is the secondary terminal
ANSI
values for example,
ANSI
Section 16
Requirements
SEMOD53771-1 v1
M11623-4 v3
M11623-6 v3
alf
(Equation 37)
M11623-14 v5
for
al
is
(Equation 38)
M11623-22 v6
can
alANSI
245