Current Transformer Requirements For Cts According To; Other Standards; Current Transformers According To Iec 61869-2, Class P, Pr; Current Transformers According To Iec 61869-2, Class Px, Pxr (And Old Iec 60044-6, Class Tps And Old British Standard, Class X) - ABB 650 series Applications Manual

Section 16
Requirements
16.1.7
16.1.7.1
16.1.7.2
16.1.7.3
298

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
standard. From different standards and available data for relaying applications it is
possible to approximately calculate a secondary e.m.f. of the CT comparable with
E . By comparing this with the required rated equivalent limiting secondary e.m.f.
al
E it is possible to judge if the CT fulfills the requirements. The requirements
alreq
according to some other standards are specified below.

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
The value of the E is approximately equal to the corresponding E
ALF
the CTs according to class P and PR must have a secondary limiting e.m.f. E
that fulfills the following:

E max E
ALF alreq
EQUATION1383 V4 EN-US
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
limiting secondary voltage U
corresponding E according to IEC 61869-2. It is not possible to give a general
al
relation between the E
knee
of the E . Therefore, the CTs according to class PX, PXR, X and TPS must have a
al
rated knee point e.m.f. E
» » »
E E E U
knee k kneeBS al
EQUATION2100 V2 EN-US

Current transformers according to ANSI/IEEE

Current transformers according to ANSI/IEEE are partly specified in different
ways. A rated secondary terminal voltage U
U is the secondary terminal voltage the CT will deliver to a standard burden at
ANSI
20 times rated secondary current without exceeding 10 % ratio correction. There
are a number of standardized U
according to the IEC 61869-2
al
(E for class PX and PXR, E
knee k
for TPS). The value of the E
al
and the E but normally the E
al
that fulfills the following:
knee
(
> ×
0.8 maximum of E
alreq
ANSI
values for example, U
ANSI
1MRK 511 423-UEN A
. Therefore,
al
for class X and the
kneeBS
is lower than the
knee
is approximately 80 %
knee
)
is specified for a CT of class C.
is 400 V for a C400
ANSI
Bay control REC650 2.2 IEC
Application manual
SEMOD53771-1 v1
M11623-4 v3
M11623-6 v4
.
ALF
ALF
(Equation 29)
M11623-14 v5
(Equation 30)
M11623-22 v6