ABB RELION REX640 Technical Manual page 1586

Section 9
Control functions
1580
Z
oTr
3
U U
0 0coil
Icoil
GUID-35FDFF49-EF05-4223-88E0-6DAB48ACF29C V1 EN
Figure 822: Simplified three-phase equivalent circuit of a compensated
distribution network
E Phase A to earth voltage of the source
A
E Phase B to earth voltage of the source
B
E Phase C to earth voltage of the source
C
U Phase A to earth voltage at busbar (=E
A
U Phase B to earth voltage at busbar (=E
B
U Phase C to earth voltage at busbar (=E
C
U Zero-sequence voltage = (U
0
U Zero-sequence voltage measured at coil
0coil
I Phase A current at the source
A
I Phase B current at the source
B
I Phase C current at the source
C
I Current through the central compensation coil
coil
Y Phase A to earth admittance of the network
A
Y Phase B to earth admittance of the network
B
Y Phase C to earth admittance of the network
C
Y Admittance of central compensation coil including the parallel resistor
coil
Z Zero-sequence impedance of the earthing transformer or the main transformer through
oTr
which the coil is connected to the network. Settings
used to input the zero-sequence impedance of the earthing / main transformer. If the
settings are applied, the controller can consider the transformer when calculating network
parameters.
Using this network model, the controller determines network parameters G
B , G , B , G
symm asymm asymm
BUSBAR
I
A
E
A
I
B
E
B
I
C
E
C
U
A
Y
coil
Y = Y /3 + Y
A symm
+ U
A o
+ U
B o
+ U
C o
+ U +U )/3
A B C
and B .
coil coil
1MRS759142 C
U
Y U
B C
d
Y = Y /3 Y
asymm B symm
)
)
)
R0Transformer and X0Transformer are
Technical Manual
I
f
Y
f
A
B
C
= Y /3
C symm
,
symm
REX640