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2 CALCULATION OF SETTINGS
flow does not allow the maximum allowable reach criteria to be met, then a "lens-shaped" characteristic
must be used. The settings of both Z4GRDREACH and Z4GCHARANG may be evaluated by using the
formula associated with the method of Figure 2–4: MAXIMUM ALLOWABLE REACH on page 2–13.
408: Z4DIRECTN - Zone 4 Direction
Z4DIRECTN determines the direction of the principle reach of the Zone 4 phase and ground distance func-
tions. The direction can be set to FORWRD or REVERS with the direction to be used dictated by the particular
scheme/application.
•
Blocking, Hybrid, POTT2 Schemes, and Reversed Third Zone Applications.
Z4DIRECTN = REVERS
•
All other schemes
Z4DIRECTN = FORWRD
409: Z4_TIMERS - Zone 4 Timers
Z4_TIMERS can be set to either YES or NO. If the Zone 4 functions are to be used to provide time-delayed
backup protection, set Z4_TIMERS = YES. Set Z4_TIMERS = NO to put both the phase and ground timers out
of service.
410: Z4P_TIME - Zone 4 Phase Time
If Z4_TIMERS = YES and if the Zone 4 phase distance functions are to provide time-delayed backup protec-
tion, then the Z4P_TIME time delay should be set long enough to coordinate with the time-delayed operation of
the appropriate zone of phase-distance relays in adjacent line sections. If Z4_TIMERS = NO then the
Z4P_TIME can be set to any value within its range with no affect on scheme operation.
411: Z4G_TIME - Zone 4 Ground Timer
If Z4_TIMERS = YES and if the Zone 4 ground distance functions are to provide time-delayed backup protec-
tion, then the Z4G_TIME time delay should be set long enough to coordinate with the time-delayed operation
of the appropriate zone of ground-distance relays in adjacent line sections. If Z4_TIMERS = NO then the
Z4G_TIME can be set to any value within its range with no affect on scheme operation.
412: Z4GRDCHAR - Zone 4 Ground Characteristic (Revision B models only)
Z4GRDCHAR can be set to either MHO or QUAD. This setting determines the measuring unit used for Zone 4
ground-distance functions. The distance function may be set as an Mho (MHO) or as a quadrilateral (QUAD).
413: Z4RGREACH - Zone 4 Resistive Ground Reach (Revision B models only)
Z4RGREACH can be set from 0.01 to 100.00 Ω for a 5 A rated relay (0.05 to 500 Ω for a 1 A rated relay). It
determines the position of the right resistive blinder for the ground distance quadrilateral characteristic to pro-
vide coverage for resistive ground faults. This setting should be a balance between desired fault resistance
coverage and load enchroachment. It should be calculated as 0.8 (if "tent" characteristics are used) or less (0.6
to 0.7 if "tent" characterstics are not used) of the positive-sequence resistance seen by the relay under maxi-
mum load conditions and unity power factor. Also, to maintain zone accuracy, it is recommended that the resis-
tive reach is not greater than 10 times the Ground Distance Reach (Protection Setting 406: Z4GRDREACH)
for this zone.
GE Power Management
LPS-D Line Protection System
2.3 PROTECTION SETTINGS
2
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