Directional Phase And Residual Overcurrent Protection - ABB 650 series Applications Manual
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1MRK 511 423-UEN A
16.1.6.3
Bay control REC650 2.2 IEC
Application manual
R
The secondary resistance of the CT (W)
ct
R
The resistance of the secondary cable and additional load (W). The loop
L
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
The burden of an IED current input channel (VA). S
R
A and S
Independent of the value of I
the following:
³
=
E
E
I
al
alreq max
k max
EQUATION1077 V2 EN-US
where
I
Maximum primary fundamental frequency current for close-in faults (A)
kmax
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
equivalent limiting secondary e.m.f. E
³
=
×
E
E
I
al
alreq
k max
EQUATION1078 V2 EN-US
where:
I
Maximum primary fundamental frequency current for close-in forward and reverse faults (A)
kmax
I
The rated primary CT current (A)
pr
I
The rated secondary CT current (A)
sr
I
The rated current of the protection IED (A)
r
R
The secondary resistance of the CT (W)
ct
R
The resistance of the secondary cable and additional load (W). The loop resistance
L
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
The burden of an IED current input channel (VA). S
R
S
=0.150 VA/channel for I
R
=0.150 VA/channel for I
R
the maximum required E
op
æ
I
S
×
×
+
+
sr
R
R
R
ç
ct
L
2
I
I
è
pr
r
that is larger than or equal to the required rated
al
below:
alreq
æ
ö
I
S
×
+
+
sr
R
R
R
ç
÷
ct
L
2
I
I
è
ø
pr
r
=5 A
r
Section 16
Requirements
=0.020 VA/channel for I
R
=5 A
r
is specified according to
al
ö
÷
ø
=0.020 VA/channel for I
=1 A and
R
r
=1
r
(Equation 27)
M11624-3 v6
(Equation 28)
297
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