ABB REL670 2.2 IEC User Manual

25.1.6.3 Breaker failure protection
M11621-3 v5
The CTs must have a rated equivalent limiting secondary e.m.f. E
al
that is larger
than or equal to the required rated equivalent limiting secondary e.m.f. E
alreq
below:
sr
R
al alreq op ct L
2
pr
r
I
S
E E 5 I R R
I
I
æ ö
³ = × × × + +
ç ÷
è ø
EQUATION1380 V2 EN-US (Equation 541)
where:
I
op
The primary operate value (A)
I
pr
The rated primary CT current (A)
I
sr
The rated secondary CT current (A)
I
r
The rated current of the protection IED (A)
R
ct
The secondary resistance of the CT (W)
R
L
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.
S
R
The burden of an IED current input channel (VA). S
R
=0.020 VA/channel for I
r
=1 A and
S
R
=0.150 VA/channel for I
r
=5 A
25.1.7 Current transformer requirements for CTs according to
other standards
SEMOD53771-1 v1
M11623-4 v3
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
according to the IEC 61869-2
standard. From different standards and available data for relaying applications it is
possible to approximately calculate a secondary e.m.f. of the CT comparable with
E
al
. By comparing this with the required rated equivalent limiting secondary e.m.f.
E
alreq
it is possible to judge if the CT fulfills the requirements. The requirements
according to some other standards are specified below.
25.1.7.1 Current transformers according to IEC 61869-2, class P, PR
M11623-6 v4
A CT according to IEC 61869-2 is specified by the secondary limiting e.m.f. E
ALF
.
The value of the E
ALF
is approximately equal to the corresponding E
al
. Therefore,
the CTs according to class P and PR must have a secondary limiting e.m.f. E
ALF
that fulfills the following:
Section 25 1MRK 506 369-UEN B
Requirements
884 Line distance protection REL670 2.2 IEC
Application manual

ABB REL670 2.2 IEC Specifications

General

Brand	ABB
Model	REL670 2.2 IEC
Category	Protection Device
Language	English