ABB Relion 670 Series Applications Manual page 349

1MRK 511 407-UUS Rev. J
23.1.7.1 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
E is approximately equal to the corresponding E
ALF
PR must have a secondary limiting e.m.f. E
E
ALF
EQUATION1383 V4 EN-US
23.1.7.2 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
23.1.7.3 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:
=
E
a lANS I
EQUATION1682 V1 EN-US
where:
Z
bANSI
V
ANSI
The CTs according to class C must have a calculated rated equivalent limiting secondary e.m.f.
E that fulfils the following:
alANSI
E
alANSI
EQUATION1384 V2 EN-US
Phasor measurement unit RES670
Application manual

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
× × + =
20 I R V 20 I
S N CT ANS I
The impedance (that is, with a complex quantity) of the standard ANSI burden for the specific C class (W)
The secondary terminal voltage for the specific C class (V)
>
maximum of E
alreq
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. Therefore, the CTs according to class P and
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
× × + × ×
R 20 I Z
S N CT S N bANS I
. The value of the
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 23
Requirements
M11623-6 v4
(Equation 105)
M11623-14 v5
for
al
is
(Equation 106)
M11623-22 v6
can
alANSI
(Equation 107)
(Equation 108)
343