ABB Relion 620 Series - Page 566

A
B
I a = 0
I
b = 0
I
b = 0
I
c = 0
I
Io
zone of
protection
C
a
b
c
I
N
I
zs1
I
zs1
I
zs1
Io
I
N
Reference is Neutral
Current
Restrain for
external fault
Operate for
internal fault
For external fault
Uzs
Figure 293: Current flow in all the CTs for an external fault
A
B
C
a
b
c
I
a = 0
I
I
b = 0
I
c = 0
I
Uzs
Io
zone of
protection
Ifault
I
N
Io
I
N
Reference is Neutral
Current
Restrain for
external fault
Operate for
internal fault
For internal fault
s
o
u
r
c
e
Figure 294: Current flow in all the CTs for an internal fault
Protection functions
1MRS757644 H
566 620 series
Technical Manual