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
260 and Figure 261. 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
Figure 260: 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
Figure 261: Through fault current from B to A: I
fA
1MRK 506 369-UUS - Section 9
Current protection
Line distance protection REL670 2.2 ANSI 505
Application manual
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