Current Transformers According To Ansi/Ieee - ABB REC650 Applications Manual

Section 16
Requirements
16.1.7.2
16.1.7.3
352
according to class P and PR must have a secondary limiting e.m.f. E
following:
>
E max E
2 max
EQUATION1383 V2 EN
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 (E
knee
secondary voltage V for TPS). The value of the E
al
according to IEC 61869-2. It is not possible to give a general relation between the E
and the E but normally the E
al
according to class PX, PXR, X and TPS must have a rated knee point e.m.f. E
fulfills the following:
= × + - ×
S TD S (1 TD S )
Old Calculated
EQUATION1893.ANSI V1 EN

Current transformers according to ANSI/IEEE

Current transformers according to ANSI/IEEE are partly specified in different ways. A
rated secondary terminal voltage V
secondary terminal 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 values for example, V
ANSI
rated equivalent limiting secondary e.m.f. E
× × +
= 20 I R V
E
S N CT
a lANS I
EQUATION1682 V1 EN
where:
Z The impedance (that is, with a complex quantity) of the standard ANSI burden for the specific C class
bANSI
(W)
V The secondary terminal voltage for the specific C class (V)
ANSI
alreq
for class PX and PXR, E
k
is approximately 80 % of the E
knee
is specified for a CT of class C. V
ANSI
is 400 V for a C400 CT. A corresponding
ANSI
alANSI
= × × +
20 I R 20 I
ANS I S N CT
1MRK 511 286-UUS A
that fulfills the
alf
for class X and the limiting
kneeBS
is lower than the corresponding E
knee
. Therefore, the CTs
al
can be estimated as follows:
× ×
Z
S N bANS I
Application manual
(Equation 99)
al
knee
that
knee
(Equation 100)
is the
ANSI
(Equation 101)