ABB REG670 Applications Manual page 342

Section 9
Current protection
336
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
currents (3I ) to the protection are calculated. For a fault at the remote line end this
0
fault current is I . In this calculation the operational state with high source impedance
fB
Z and low source impedance Z
A
fault current is I . In this calculation the operational state with low source impedance
fA
Z and high source impedance Z
A
A
Z
~
A
IED
IEC09000022 V1 EN
Figure 177: Through fault current from A to B: I
A
Z
~
A
IED
Fault
IEC09000023 V1 EN
Figure 178: Through fault current from B to A: I
The function shall not operate for any of the calculated currents to the protection. The
minimum theoretical current setting (Imin) will be:
 

Im in MAX I , I
f A fB
EQUATION284 V2 EN
Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062
177
should be used. For the fault at the home busbar this
B
should be used.
B
I
fB
B
Z Z
L B
Fault
fB
I
fA
B
Z
Z
L B
fA
1MRK 502 071-UEN -
and Figure 178. The residual
~
IEC09000022-1-en.vsd
~
IEC09000023-1-en.vsd
(Equation 187)
Application manual