ABB 615 series Technical Manual page 382

Section 4
Protection functions
376
E
A
E
B
E
C
R
n
VG
Uo
L
cc
R
cc
Reverse fault:
Yo ≈ ‐j*I
eFd
GUID-2C307D73-EF4A-479A-A6E5-47CAC730188C V1 EN
Figure 176: Admittance calculation during a reverse fault
R Resistance of the parallel resistor
CC
L Inductance of the compensation coil
CC
R Resistance of the neutral grounding resistor
n
Y Phase-to-ground admittance of the protected feeder
Fd
Y Phase-to-ground admittance of the background network
Bg
For example, in a 15 kV compensated network with the magnitude of the ground-fault
current in the protected feeder being 10 A (Rf = 0 Ω), the theoretical value for the
measured admittance during a ground fault in the reverse direction, that is, outside the
protected feeder, can be calculated.
IG
Io
A B C
Protected feeder
~
~
~
Background network
Im(Yo)
Re(Yo)
/U Vph
ph
1MAC059074-MB A
Y
Fd
Reverse
Fault
Y
Bg
(I ‐ I )
I
eTot eFd
eFd
615 series ANSI
Technical Manual