Non-Directional Instantaneous And Definitive Time, Phase And Residual Overcurrent Protection - ABB REL650 Applications Manual

Section 18
Requirements
18.1.6.3
494
I
×
³ = × ×
E E 5 I s n
op
a l a lre q
I
pn
EQUATION1677 V1 EN
where:
I The primary operate value (A)
op
I The rated primary CT current (A)
pn
I The rated secondary CT current (A)
sn
I The nominal current of the protection IED (A)
n
R
The secondary resistance of the CT (W)
CT
R The resistance of the secondary cable and additional load (W). The loop resistance containing the
L
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 The burden of an IED current input channel (VA). S
R
channel for I =5 A
r
Non-directional instantaneous and definitive time, phase and residual
overcurrent protection
The CTs must have a rated equivalent secondary e.m.f. E
the required secondary e.m.f. E
I
×
³ = ×
E E 1.5 I s n
op
a l a lre q
I
pn
EQUATION1678 V1 EN
where:
I The primary operate value (A)
op
I The rated primary CT current (A)
pn
I The rated secondary CT current (A)
sn
I The nominal current of the protection IED (A)
n
R The secondary resistance of the CT (W)
CT
R
The resistance of the secondary cable and additional load (W). The loop resistance containing the
L
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 The burden of an IED current input channel (VA). S
R
channel for I =5 A
r
æ ö
S
+ +
R R R
ç ÷
CT L
2
è I ø
n
R
below:
alreq
æ ö
S
× + +
R R R
ç ÷
CT L
2
è I ø
n
R
1MRK 506 334-UUS A
=0.010 VA/channel for I =1 A and S
r
that is larger than or equal to
al
=0.010 VA/channel for I =1 A and S
r
Application manual
(Equation 180)
=0.250 VA/
R
(Equation 181)
=0.250 VA/
R