ABB REG670 - Page 342

GlobalBaseSel: This is used to select GBASVAL function for reference of base
values.
The basic requirement is to assure selectivity, that is EFPIOC 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-earth faults and phase-to-phase-
to-earth faults shall be calculated as shown in Figure
177 and Figure 178. 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
IEC09000022-1-en.vsd
IEC09000022 V1 EN
Figure 177: Through fault current from A to B: I
fB
IEC09000023-1-en.vsd
~ ~
Z
A
Z
B
Z
L
A B
IED
I
fA
Fault
IEC09000023 V1 EN
Figure 178: Through fault current from B to A: I
fA
The function shall not operate for any of the calculated currents to the protection. The
minimum theoretical current setting (Imin) will be:


Im ,
f
AfB
in MAX I I
EQUATION284 V2 EN
(Equation 187)
Section 9 1MRK 502 071-UEN -
Current protection
336 Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062
Application manual