ABB 615 Series - Page 385

background network. Theoretically, the measured admittance is located in the first
quadrant in the admittance plane, see Figure 177.
Im(Yo)
Re(Y
o)
Forwardfault,
ungroundednetwork:
Y
o≈j*(I
eTot
‐I
eFd
)/U
ph
Forwardfault,compensatednetwork:
Y
o≈(I
rcc
+j*(I
eTot
*(1‐ K)‐ I
eFd
))/U
ph
Under‐ comp.(K<1)
Resonance(K=1)
Over‐ comp.(K>1)
Reversefault:
Y
o≈‐j*I
eFd
/U
ph
Forward fault ,
high resist ance earthed network:
Y
o ≈(I
Rn
+j*(I
eTot
‐I
eFd
))/U
ph
~
~
~
AB C
E
A
E
B
E
C
Io 
Forward
Fault
L
cc
R
cc
I
eFd
I
eTot
(I
eTot
‐ I
eFd
)
Uo 
R
n
Protectedfeeder 
Back ground network
Y
Fd
Y
Bg
VG
Vph
Vph
Vph
Vph
IG
GUID-99A93925-B7EF-4154-A90B-AE3DFC3ABFA1 V1 EN
Figure 177: Admittance calculation during a forward fault
1MAC059074-MB A Section 4
Protection functions
615 series ANSI 379
Technical Manual