ABB REG670 - Page 334

i1Mag
i2Mag
i3Mag
a==b
a
b
a==b
a
b
a==b
a
b
MAX
&
&
A
B
C
startPh1
startPh2
startPh3
&
&
&
start
³
1
IEC11000307_1_en.vsd
1
³
IEC11000307 V1 EN
Figure 151: Logic diagram for the selection of the maximum current loop
The phase-to-earth voltage is compensated with zero sequence voltage in order to
avoid the function operating for earth faults in zone 1, that is, complete generator
stator winding and LV winding of the power transformer.
The reach settings for zone 2 can be provided using the Z2Fwd, Z2Rev and
ImpedanceAng settings. The Z2Fwd is forward reach setting and Z2Rev is reverse
reach setting. The offset mho characteristic for phase-to-earth loop is shown in Figure
152. The offset mho characteristics for phase-to-phase loop is shown in Figure 153.
ß
12
I
L Z Fwd
11 012Ucomp UL E U IL Z Fwd
21 012Ucomp UL E U IL Z REV
12IL Z REV
1
I
LjX
1
I
LR

IEC11000299-2-en.vsd
IEC11000299 V2 EN
Figure 152: Simplified offset mho characteristics for L1-to-E fault in zone 2
Section 7 1MRK502052-UEN B
Impedance protection
328
Technical manual