ABB Relion 670 Series Applications Manual page 610

Section 25
Requirements
R
ct
R
L
S
R
Independent of the value of I
following:
³
E E
al
EQUATION1077 V2 EN-US
where
I
kmax
25.1.6.4 Directional phase and residual overcurrent protection
If the directional overcurrent function is used the CTs must have a rated equivalent limiting
secondary e.m.f. E
secondary e.m.f. E
³
E E
al
EQUATION1078 V2 EN-US
where:
I
kmax
I
pr
I
sr
I
r
R
ct
R
L
S
R
25.1.7 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
available data for relaying applications it is possible to approximately calculate a secondary
604
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
I =1 A and S =0.150 VA/channel for I
r R
the maximum required E
op
æ
I
= × ×
sr
I
ç
alreq max k max
I
è
pr
Maximum primary fundamental frequency current for close-in faults (A)
that is larger than or equal to the required rated equivalent limiting
al
below:
alreq
æ
I
= × ×
sr
I R
ç
alreq k max ct
I
è
pr
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 61869-2 standard. From different standards and
al
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=5 A
r
ö
S
+ +
R
R R
÷
ct L
2
I
ø
r
ö
S
+ +
R
R
÷
L
2
I
ø
r
=0.020 VA/channel for I
R
1MRK 511 401-UEN Rev. K
=0.020 VA/channel for
R
is specified according to the
al
=1 A and S
r
Bay control REC670
Application manual
(Equation 200)
M11624-3 v6
(Equation 201)
=0.150 VA/
R
SEMOD53771-1 v1
M11623-4 v3