ABB 615 series Technical Manual page 560

Section 4
Protection functions
554
branch. R increases the impedance of the protection relay; hence the name high-
s
impedance differential scheme.
GUID-1AB5D686-3B9C-413F-9D0A-215BFCA224B4 V1 EN
Figure 278: Phase-segregated bus differential protection based on high-impedance
principle
CT secondary winding resistances (R
shown in Figure 279.
Figure 279 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.
) and connection wire resistances (R
in
is the maximum wiring resistance concerning all
m2
1MAC059074-MB A
/2) are also
m
) is not included.
u
and R .
m1 m2
615 series ANSI
Technical Manual