Current Transformers According To Iec 60044-1, Class Px, Iec 60044-6, Class Tps (And Old British Standard, Class X); Current Transformers According To Ansi/Ieee - ABB RET670 Applications Manual

Section 2
Requirements
2.1.7.2
2.1.7.3
28
>
E max E
2 max
EQUATION1383 V2 EN
Current transformers according to IEC 60044-1, class PX, 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
voltage V for TPS). The value of the E
al
according to IEC 60044-6. It is not possible to give a general relation between the E
and the E but normally the E
al
according to class PX, X and TPS must have a rated knee-point e.m.f. E
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 U values for example, V
ANSI
corresponding rated equivalent limiting secondary e.m.f. E
follows:
× × +
= 20 I R V
E
S N CT
a lANS I
EQUATION1682 V1 EN
where:
Z The impedance (that is, complex quantity) of the standard ANSI burden for the specific C class (W)
bANSI
V The secondary terminal voltage for the specific C class (V)
ANSI
alreq
for class PX, E
k kneeBS
is lower than the corresponding E
knee
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
ANSI
= × × +
20 I R 20 I
ANS I S N CT
1MRK504116-UUS C
for class X and the limiting secondary
. Therefore, the CTs
al
knee
can be estimated as
alANSI
× ×
Z
S N bANS I
Application manual
(Equation 11)
al
knee
that fulfills
(Equation 12)
is the
ANSI
(Equation 13)