EnableZone2 = “Max Curr PhG”
T
F
OR
AND
LoadEnchMod2
T
F
1
Measuring Loop
phase-to-ground
(ZA<,ZB<,ZC<)
EnableZone2
Z2Fwd
Z2Rev
LineAngle
Max Curr
Loop logic
Zero
sequence
Voltage
Compensation
OpModeZ2
Timer
tZ2
Load
Encroachment
RLd
LdAngle
V3P
I3P
BLOCK
BLKZ
PU_Z2
TRZ2
ANSI11000298_2_en.vsd
Measuring Loop
phase-to-phase
(ZAB<,ZBC<,ZCA<)
EnableZone2
Z2Fwd
Z2Rev
LineAngle
AND
ANSI11000298 V2 EN-US
Figure 239: Block diagram of zone 2
Zone 2 can be used to cover up to the HV side of the transformer and the HV bus bar. It also covers
to some degree, the stator winding. The time to trip is provided in order to coordinate with the
zone 1 element on the shortest outgoing line from the bus.
Zone 2 coverage provides backup for the phase-to-phase and three-phase faults in generator. It
also protects LV winding of generator transformer and phase-to-ground, phase-to-phase and
three-phase faults in the HV side of transformer and bus. A separate maximum current feature is
provided in phase-to-ground loop selection which gives correct reach measurement for phase-to-
phase fault on HV side. Zero sequence compensation for the phase voltages is given in phase-to-
ground measuring loops in order to prevent operation for the stator ground faults.
Zone 2 can be selected for different measuring loops using the setting
OpModeZ2
. The
OpModeZ2
can be selected as
Disabled
or
PP Loops
or
EnhancedReach
. If the
OpModeZ2
is selected as
EnhancedReach
, the loop used for measurements is the phase-to-earth measuring loop (AG, BG
and CG) which is with maximum phase current of all the three phase currents.
Figure
240 shows the logic to detect the phase to ground loop with maximum phase current.
1MRK 502 066-UUS B Section 7
Impedance protection
441
Technical manual
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