Current Transformer Requirements For Cts According To Other Standards; Current Transformers According To Iec 60044-1, Class P, Pr; Current Transformers According To Iec 60044-1, Class Px, Iec 60044-6, Class Tps (And Old British Standard, Class X) - ABB Relion 650 Series Applications Manual

1MRK 504 124-UEN B
³
E E
al
EQUATION1078 V1 EN-US
where:
I
kmax
I
pn
I
sn
I
r
R
CT
R
L
S
R
19.1.7 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
secondary e.m.f. E
available data for relaying applications it is possible to approximately calculate a secondary
e.m.f. of the CT comparable with E
E it is possible to judge if the CT fulfills the requirements. The requirements according to
alreq
some other standards are specified below.
19.1.7.1

Current transformers according to IEC 60044-1, class P, PR

A CT according to IEC 60044-1 is specified by the secondary limiting e.m.f. E
the E
2max
the CTs according to class P and PR must have a secondary limiting e.m.f. E
following:
E
2 max
EQUATION1383 V1 EN-US
19.1.7.2 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
TPS). The value of the E
not possible to give a general relation between the E
approximately 80 % of the E
rated knee-point e.m.f. E
Transformer protection RET650
Application manual
æ
I
= × ×
sn
I R
ç
alreq k max
I
è
pn
Maximum primary fundamental frequency current for close-in forward and reverse faults (A)
The rated primary CT current (A)
The rated secondary CT current (A)
The rated current of the protection IED (A)
The secondary resistance of the CT (W)
The resistance of the secondary cable and additional load (W). The loop resistance containing the
phase and neutral wires, must be used for faults in solidly earthed systems. The resistance of a single
secondary wire should be used for faults in high impedance earthed systems.
The burden of an IED current input channel (VA). S
channel for I =5 A
r
according to the IEC 60044-6 standard. From different standards and
al
is approximately equal to the corresponding E
>
max imum of E
alreq
(E for class PX, E
knee k
is lower than the corresponding E
knee
. Therefore, the CTs according to class PX, X and TPS must have a
al
that fulfills the following:
knee
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ö
S
+ +
R
R
÷
CT L
2
I
ø
r
=0.010 VA/channel for I
r
. By comparing this with the required secondary e.m.f.
al
for class X and the limiting secondary voltage U
kneeBS
knee
=1 A and S
r
2max
according to IEC 60044-6. Therefore,
al
2max
according to IEC 60044-6. It is
al
and the E but normally the E
al
Section 19
Requirements
(Equation 106)
=0.250 VA/
r
SEMOD53771-1 v1
M11623-4 v2
M11623-6 v1
. The value of
that fulfills the
(Equation 107)
M11623-14 v3
for
al
is
knee
267