ABB Relion 670 Series Applications Manual page 495

1MRK 505 370-UUS Rev. K
R
ct
R
L
S
R
Independent of the value of I
³
E E
a l a lre q ma x
EQUATION1680 V1 EN-US
where
I
kmax
21.1.7 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 limiting secondary
e.m.f. E
al
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. E
if the CT fulfills the requirements. The requirements according to some other standards are specified
below.
21.1.7.1 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
is approximately equal to the corresponding E
have a secondary limiting e.m.f. E
E
ALF
EQUATION1383 V4 EN-US
21.1.7.2 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 (E
knee k
value of the E
a general relation between the E
Busbar protection REB670
Application manual
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 grounded systems. The resistance of a single secondary wire should be
used for faults in high impedance grounded systems.
The burden of an IED current input channel (VA). S
A and S =0.150 VA/channel for I
R
the maximum required E
op
æ
I
×
= × +
I s n R
ç
k ma x
CT
I
è
pn
Maximum primary fundamental frequency current for close-in faults (A)
according to the IEC 61869-2 standard. From different standards and available data for relaying
ALF

max E
alreq
for class PX and PXR, E
kneeBS
is lower than the corresponding E
knee
knee
© 2017 - 2021 Hitachi Power Grids. All rights reserved
=5 A
r
is specified according to the following:
al
ö
S
+
R R
÷
L
2
I
ø
n
. Therefore, the CTs according to class P and PR must
al
that fulfills the following:
for class X and the limiting secondary voltage V
according to IEC 61869-2. It is not possible to give
al
and the E but normally the E
al
=0.020 VA/channel for I =1
R r
it is possible to judge
alreq
. The value of the E
ALF
for TPS). The
al
is approximately 80 % of the E
knee
Section 21
Requirements
(Equation 101)
SEMOD53771-1 v1
M11623-4 v3
.
al
M11623-6 v4
ALF
(Equation 102)
M11623-14 v5
.
al
489