ABB rec670 - Directional Phase and Residual Overcurrent Protection

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:
sn R
al 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 CT
s must have a rated equivalent
limiting secondary e.m.f. E
al
that is lar
ger than or equal to the required rated equivalent
limiting secondary e.m.f. E
alreq
below:
sn
R
al a lreq CT L
2
pn n
k max
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