GE P24DM - Figure 42: Earth Fault in Petersen Coil Earthed System; Figure 43: Distribution of Currents During a Phase C Fault

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jX
L
AN
L
V
jX
AB
C
V
jX

ac
C
V
jX

0
AN
f B C
L
AN
B C
L
V
I I I
jX
V
if I I
jX
   
  
Source
Petersen
Coil
Current vectors for A phase fault
If
-IC
A
BC
N
-I
B
I
L
V
AB
V
AC
-I
B
-IC
(=I
L
)
(=-I
B
) (=-I
C
)
-jX
C
-jX
C
-jX
C
Figure 42: Earth fault in Petersen Coil earthed system
Consider a radial distribution system ear
thed using a Petersen Coil with a phase to earth fault on phase C, shown
in the figure below:
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I
A1
I
B1
I
R1
-jX
C1
I
H1
I
A2
I
B2
I
R2
I
L
-jX
C2
jXL
I
H 2
I
A3
IB3
IC3 = IF
-jX
C3
I
R3
I
F
IH3
I
H1
+ I
H2
I
L
= I
F
+ I
H1
+ I
H2
+ I
H3
Figure 43: Distribution of currents during a Phase C fault
Assuming that no r
esistance is present in X
L
or X
C
, the resulting phasor diagrams will be as shown in the figure
below:
Chapter 6 - Current Protection Functions P24xM
116 P24xM-TM-EN-2.1