2-22
ALPS Advanced Line Protection System
GE Power Management
2.3 PROTECTION SETTINGS
2 CALCULATION OF SETTINGS
2
409: Z4_TIMERS - Z4 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 protec-
tion, set Z4_TIMERS = YES. Set Z4_TIMERS = NO to put both the phase and ground timers out of service.
410: Z4P_TIME - Z4 Phase Timer
If Z4_TIMERS = YES and if the Zone 4 phase distance functions are to provide time delayed backup protection, 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 - Z4 Ground Timer
If Z4_TIMERS = YES and if the Zone 4 ground distance functions are to provide time delayed backup protection, 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 dis-
tance 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 provide coverage for resistive
ground faults. This setting should be a balance between desired fault resistance coverage and load encroachment. It
should be calculated as 0.8 (if “tent” characteristics are used) or less (0.6 to 0.7 if “tent” characteristics are not used) of the
positive-sequence resistance seen by the relay under maximum load conditions and unity power factor. Also, to maintain
zone accuracy, it is recommended that the resistive reach is not greater than 10 times the Ground Distance Reach (Protec-
tion Setting 406: Z4GRDREACH) for this zone.
2.3.6 CURSUPVISN
501: IT_PICKUP - Trip Supervision Current
502: IB_PICKUP - Block Supervision Current
•
Step Distance, PUTT, POTT1 and POTT2 Schemes: These two overcurrent functions provide supervision for the dis-
tance functions. IT is also used in the trip bus seal-in circuit. To obtain maximum sensitivity, the following settings are
proposed:
IT_PICKUP = minimum; IB_PICKUP = minimum
•
Blocking and Hybrid Schemes: The IT overcurrent function provides supervision for the tripping-zone distance func-
tions, and is also used in the trip bus seal-in circuit. The IB overcurrent function provides supervision for the reversed
phase and ground distance functions. For a Blocking or Hybrid scheme, the local IT and remote IB functions must
coordinate. This is accomplished by setting IB more sensitively (with a lower pickup) than IT. To obtain maximum sen-
sitivity, the following settings are proposed:
IB_PICKUP = minimum
IT_PICKUP = 1.3 x IB_PICKUP
R
+
I
c
where: IB_PICKUP
R
= pickup setting of IB function at remote terminal of line
I
c
= positive-sequence line charging current (include effect of any non-switched shunt reactors)
503: IPT_PICKUP - GDOC Trip Current
504: IPB_PICKUP - GDOC Block Current
The IPT and IPB functions are placed in service whenever Z2GRDCHAR is set to MHO, GDOC, or MHOGDOC. The use of
these functions will provide more sensitive protection for high resistance ground faults than can be obtained with ground
distance functions alone.
