Figure 42: Earth Fault In Petersen Coil Earthed System; Figure 43: Distribution Of Currents During A Phase C Fault - GE P24DM Technical Manual

Chapter 6 - Current Protection Functions
Source
V
AN
jX
L
(=I )
L
Petersen
jX
L
Coil
V00631

Figure 42: Earth fault in Petersen Coil earthed system

Consider a radial distribution system earthed using a Petersen Coil with a phase to earth fault on phase C, shown
in the figure below:
V00632

Figure 43: Distribution of currents during a Phase C fault

Assuming that no resistance is present in X
below:
116
-I
B
-I
C
V
AN
   
I I I
f B C
j X
L
V
AN
  
0 i f I I
B C
I j X
f
L
I
L
jX
L
I = I + I
L F
or X
L C
V V
 AB  ac
jX jX
C C
(=-I ) (=-I )
B C
-jX -jX -jX
C C C
I
A1
I
B1
I
R1
-jX
C1
I
H1
I
A2
I
B2
I
R2
-jX
I
H 2
I
A3
I
B3
I = I
C3 F
I
R3
-jX
I
F
I
I
H3
+ I + I
H1
H1 H2 H3
, the resulting phasor diagrams will be as shown in the figure
-I
C
A
-I
B
V
AC
N
C
Current vectors for A phase fault
C2
C3
+ I
H2
P24xM
I
L
V
AB
B
P24xM-TM-EN-2.1