ABB ret650, Applications Manual

Page: 124 / 392

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
48 and Figure 49 . 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-US
Figure 48: 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-US
Figure 49: 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 ,
fA fB
in MAX I I

EQUATION284 V2 EN-US
(Equation 26)
Section 7
1MRK 504 169-UEN A
Current protection
118 Transformer protection RET650 2.2 IEC
Application manual