BLOCK
1
&
LoadEnchModZ2
T
F
1
Measuring Loop
EnhancedReach
OpModeZ2
Z2Fwd
Z2Rev
ImpedanceAng
Zero
sequence
Voltage
Compensation
Load
Encroachment
RLd
ArgLd
U3P
I3P
BLKZ
STZ2
TRZ2
IEC11000298-3-en.vsd
Measuring Loop
phase-to-phase
(ZL1L2<,ZL2L3<,ZL3L1<)
OpModeZ2
Z2Fwd
Z2Rev
ImpedanceAng
tZ2
t
IEC11000298 V3 EN
Figure 150: 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-earth,
phase-to-phase and three-phase faults in the HV side of transformer and the bus. A
separate maximum current feature is provided in phase-to-earth 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-earth measuring loops in
order to prevent operation for the stator earth faults.
Zone 2 can be selected for different measuring loops using the setting OpModeZ2. The
OpModeZ2 can be selected as Off or PP Loops or EnhancedReach. If the OpModeZ2
is selected as EnhancedReach, the loop used for measurements is the phase-to-earth
measuring loop (L1E, L2E and L3E) which is with maximum phase current of all the
three phase currents.
Figure
151 shows the logic to detect the phase to earth loop with maximum phase
current.
1MRK502052-UEN B Section 7
Impedance protection
327
Technical manual
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