ABB RELION 620 Series Technical Manual page 476

Section 4
Protection functions
470
GUID-1AB5D686-3B9C-413F-9D0A-215BFCA224B4 V1 EN
Figure 218: Phase-segregated bus differential protection based on high-impedance
principle
CT secondary winding resistances (R
shown in Figure 219.
Figure 219 demonstrates a simplified circuit consisting only of one incoming and
outgoing feeder. To keep it simple, the voltage-dependent resistor (R
The wiring resistances are presented as total wiring resistances R
R is the maximum wiring resistance concerning all incoming feeder
m1
sets, whereas R
outgoing feeder sets.
The lower part of Figure 219
and no CT saturation.
) and connection wire resistances (R
in
is the maximum wiring resistance concerning all
m2
shows the voltage balance when there is no fault in the system
1MAC504801-IB E
/2) are also
m
) is not included.
u
and R .
m1 m2
620 series ANSI
Technical Manual