ABB RELION RET670, Applications Manual

Page: 538 / 1016

M12762-6 v8
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
265 and Figure 266 . The
residual currents (3I
0
) to the protection are calculated. For a fault at the remote line end
this fault current is I
fB
. In this calculation the operational state with high source
impedance Z
A
and low source impedance Z
B
should be used. For the fault at the home
busbar this fault current is I
fA
. In this calculation the operational state with low source
impedance Z
A
and high source impedance Z
B
should be used.
~ ~
Z
A
Z
B
Z
L
A B
IED
I
fB
Fault
ANSI09000022-1-en.vsd
ANSI09000022 V1 EN-US
Figure 265: Through fault current from A to B: I
fB
ANSI09000023-1-en.vsd
~ ~
Z
A
Z
B
Z
L
A B
IED
I
fA
Fault
ANSI09000023 V1 EN-US
Figure 266: Through fault current from B to A: I
fA
Section 9
1MRK 504 163-UUS A
Current protection
532 Transformer protection RET670 2.2 ANSI
Application manual