ABB Relion 670 Series Applications Manual page 512

Section 22
Requirements
³
E E
a l a lre q
EQUATION1677 V1 EN-US
where:
I
op
I
pr
I
sr
I
n
R
ct
R
L
S
R
22.1.6.2 Non-directional instantaneous and definitive time, phase and residual
overcurrent protection
The CTs must have a rated equivalent limiting secondary e.m.f. E
the required rated equivalent limiting secondary e.m.f. E
³
E E
a l a lre q
EQUATION1678 V1 EN-US
where:
I
op
I
pr
I
sr
I
n
R
ct
R
L
S
R
506
æ
I
×
= × × +
s n
5 I R R
ç
op
CT
I
è
pn
The primary operate value (A)
The rated primary CT current (A)
The rated secondary CT current (A)
The nominal current of the protection IED (A)
The secondary resistance of the CT (W)
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.
The burden of an IED current input channel (VA). S
for I =5 A
r
æ
I
×
= × × +
1.5 I s n R
ç
op
CT
I è
pn
The primary operate value (A)
The rated primary CT current (A)
The rated secondary CT current (A)
The nominal current of the protection IED (A)
The secondary resistance of the CT (W)
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.
The burden of an IED current input channel (VA). S
for I =5 A
r
ö
S
+
R
÷
L
2
I
ø
n
=0.020 VA/channel for I
R
alreq
ö
S
+
R R
÷
L
2
I ø
n
=0.020 VA/channel for I
R
1MRK 511 358-UUS A
=1 A and S =0.150 VA/channel
r R
that is larger than or equal to
al
below:
=1 A and S =0.150 VA/channel
r R
Application manual
(Equation 132)
M11622-3 v5
(Equation 133)