ABB REB650 - Non-Directional Instantaneous and Definitive Time, Phase and Residual Overcurrent Protection

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