sr
R
al
alreq
op
ct
L
2
pr
r
I
S
E
E
5 I
R
R
I
I
æ
ö
³
= ×
×
×
+
+
ç
÷
è
ø
EQUATION1380 V2 EN-US
(Equation 42)
where:
I
op
The primary operate value (A)
I
pr
The rated primary CT current (A)
I
sr
The rated secondary CT current (A)
I
r
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 earthed systems.
The resistance of a single secondary wire should be used for faults in high impedance
earthed 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
18.1.6.2
Non-directional instantaneous and definitive time, phase and residual
overcurrent protection
M11622-3 v5
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:
sr
R
al
alreq
op
ct
L
2
pr
r
I
S
E
E
1,5 I
R
R
I
I
æ
ö
³
=
×
×
×
+
+
ç
÷
è
ø
EQUATION1381 V2 EN-US
(Equation 43)
where:
I
op
The primary operate value (A)
I
pr
The rated primary CT current (A)
I
sr
The rated secondary CT current (A)
I
r
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 earthed systems.
The resistance of a single secondary wire should be used for faults in high impedance
earthed 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 18
1MRK 505 388-UEN B
Requirements
298
Busbar protection REB650 2.2 IEC
Application manual
Summary of Contents for REB650
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