ABB RELION REX640 Technical Manual page 756

Protection functions
Figure 429: Current flow in all the CTs for an external fault
s
A
o
u
B
r
c
C
e
Io
Figure 430: Current flow in all the CTs for an internal fault
756
I
zs1
A
I
zs1
B
I
zs1
C
Uzs Io
Operate for
internal fault
Ifault
For internal fault
zone of
protection
For external fault
Restrain for
external fault
zone of
protection
Uzs
Io
Operate for
external fault
internal fault
1MRS759142 F
I
N
Io
I
N Reference is Neutral
Current
I
N
I
N
Reference is Neutral
Current
Restrain for
Technical Manual
I
a = 0
a
I I
b = 0 b = 0
b
I I
c = 0
c
I I
a = 0
a
I I
b = 0
b
I
c = 0
c
REX640