Due to inaccuracies in voltage and current measurement, the small
real part of the calculated neutral admittance may appear as
positive, which brings the measured admittance in the fourth
quadrant in the admittance plane. This should be considered when
setting the admittance characteristic.
~
~
~
A B C
U
o
E
A
E
B
E
C
Io
Reverse
Fault
Y
Fd
L
cc
R
cc
Y
Bg
I
eFd
(I
eTot
- I
eFd
)
R
n
Protected feeder
Background network
Im(Yo)
Re(Y
o)
Reverse fault:
Y
o ≈ -j*I
eFd
/U
ph
GUID-B852BF65-9C03-49F2-8FA9-E958EB37FF13 V1 EN
Figure 157: Admittance calculation during a reverse fault
R
CC
Resistance of the parallel resistor
L
CC
Inductance of the compensation coil
R
n
Resistance of the neutral earthing resistor
Y
Fd
Phase-to-earth admittance of the protected feeder
Y
Bg
Phase-to-earth admittance of the background network
1YHT530004D05 D Section 4
Protection functions
615 series 315
Technical Manual
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