ABB Relion REC670, Applications Manual

Page: 640 / 658

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 grounded systems. The resistance of a single secondary wire should be
used for faults in high impedance grounded 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
Independent of the value of I
op
the maximum required E
al
is specified according to the
following:
s n R
a l a lre q ma x CT L
2
pn n
k ma x
I S
E E I R R
I I
³ = × + +
æ ö
×
ç ÷
è ø
EQUATION1680 V1 EN-US
(Equation 131)
where
I
kmax
Maximum primary fundamental frequency current for close-in faults (A)
24.1.6.4 Directional phase and residual overcurrent protection
M11624-3 v6
If the directional overcurrent function is used 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:
s n R
a l a lre q CT L
2
pn n
k ma x
I S
E E I R R
I I
³ = × + +
æ ö
×
ç ÷
è ø
EQUATION1681 V1 EN-US
(Equation 132)
where:
I
kmax
Maximum primary fundamental frequency current for close-in forward and reverse faults (A)
I
pr
The rated primary CT current (A)
I
sr
The rated secondary CT current (A)
I
n
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 grounded systems. The resistance of a
single secondary wire should be used for faults in high impedance grounded 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
Section 24
1MRK 511 401-UUS A
Requirements
634 Bay control REC670 2.2 ANSI
Application manual