ABB Relion 650 Series Applications Manual page 248

Section 16
Requirements
³
E E
al
EQUATION-2431---ANSI V1 EN-US
where:
V
s
I
kmax
I
pn
I
sn
R
CT
R
L
All CTs to the same protection should have identical turn ratios. Consequently auxiliary CTs cannot
normally be used. The IED must be provided with separate cores.
16.1.6.2 Breaker failure protection
The CTs must have a rated equivalent secondary e.m.f. E
required secondary e.m.f. E
³
E E
a l a lre q
EQUATION1677 V1 EN-US
where:
I
op
I
pn
I
sn
I
n
R
CT
R
L
S
R
242
I
= × = × ×
2 V 2 I sn
alreq s tmax
I
pn
Set operate value to the voltage relay (V)
Maximum primary fundamental frequency fault current for through fault current for external faults (A)
The rated primary CT current (A)
The rated secondary CT current (A)
The secondary resistance of the CT (Ω)
The resistance of the secondary cable from the CT up to a common junction point (Ω). The loop resistance
containing the phase and neutral wires, must be used for faults in solidly grounded systems and the
resistance of a single-phase wire should be used for faults in high impedance grounded systems.
below:
alreq
æ
I
×
= × × +
5 I s n R
ç
op
CT
I
è
pn
The primary operate value (A)
The rated primary CT current (A)
The rated secondary CT current (A)
The nominal 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 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
for I =5 A
r
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× +
(R R )
CT L
ö
S
+
R R
÷
L
2
I
ø
n
=0.010 VA/channel for I
R
that is larger than or equal to the
al
=1 A and S
r
Busbar protection REB650
1MRK 505 287-UUS B
(Equation 31)
M11621-3 v4
(Equation 32)
=0.250 VA/channel
R
Application manual