ABB RELION RET670 Applications Manual page 538

Section 9
Current protection
532
Common base IED values for primary current (IBase), primary voltage (VBase) and
primary power (SBase) are set in the global base values for settings function
GBASVAL.
GlobalBaseSel: This is used to select GBASVAL function for reference of base values.
The basic requirement is to assure selectivity, that is EFPIOC (50N) shall not be
allowed to operate for faults at other objects than the protected object (line).
For a normal line in a meshed system single phase-to-ground faults and phase-to-
phase-to-ground faults shall be calculated as shown in Figure
residual currents (3I ) to the protection are calculated. For a fault at the remote line end
0
this fault current is I . In this calculation the operational state with high source
fB
impedance Z and low source impedance Z
A
busbar this fault current is I
impedance Z and high source impedance Z
A
A
Z
~
A
IED
ANSI09000022 V1 EN-US
Figure 265: Through fault current from A to B: I
A
Z
~ A
IED
Fault
ANSI09000023 V1 EN-US
Figure 266: Through fault current from B to A: I
should be used. For the fault at the home
B
. In this calculation the operational state with low source
fA
should be used.
B
I
fB
B
Z
L
Fault
fB
I
fA
B
Z
L
fA
1MRK 504 163-UUS A
265 and Figure 266. The
Z
~
B
ANSI09000022-1-en.vsd
Z
B ~
ANSI09000023-1-en.vsd
Transformer protection RET670 2.2 ANSI
Application manual
M12762-6 v8