2-
14
LPS-O Line Protection System GE Power Management
2.3 PROTECTION SETTINGS 2 CALCULATION OF SETTINGS
2
403: Z4PCHARANG - Z4 Phase Characteristic
Angle
This setting determines the characteristic shape and, consequently, the area of resistance coverage provided
by the Zone 4 phase distance functions.
Z4PCHARANG
can be set to 80° to 120° in 5° steps. A 90° setting is
recommended and settings lower than 90° should not be used. If the desired reach,
Z4PHREACH
, with a 90°
characteristic and with maximum load flow does not allow the maximum allowable reach criteria to be met,
then a "lens-shaped" characteristic must be used. The settings of both
Z4PHREACH
and
Z4PCHARANG
may
be evaluated by using the maximxul allowable reach formula associated with Figure 2–2: MAXIMUM ALLOW-
ABLE REACH on page 2–9.
405: Z4_TIMERS - Z4 Timers
The choice of settings is YES or NO. Set
Z4TIMERS
= YES if the Zone 4 phase distance time delay is to be
used, otherwise set
Z4TIMERS
= NO.
406: Z4P_TIME - Zone 4 Phase Timer
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.
2.3.6 CURSUPVISN
501: IT_PICKUP - Trip Supervision Current
502: IB_PICKUP - Block Supervision Current
These two overcurrent functions provide supervision for the phase distance 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
503: IPT_PICKUP - Ground Overcurrent (Forward)
504: IPB_PICKUP - Ground Overcurrent (Reverse)
505: IPBKFACTOR - IPB I1 Restraint
The
IPT_PICKUP
,
IPB_PICKUP
, and
IPBKFACTOR
settings have no significance in the step distance scheme
used with the LPS-O. However the IPT and IPB functions are available for general purpose use in the LPS-O
for configurable outputs. The settings are not user adjustable and are fixed to values shown in the Table below.
506: NT_OFFSET: NT/NB Offset
The NT/NB functions use an offset to provide a reliable polarizing quantity for the conditions shown in Figure
2–6: NT/NB FUNCTIONS below.
Table 2–4: FIXED VALUES FOR PROTECTION SETTINGS 503 TO 505
SETTING # MNEMONIC DESCRIPTION VALUE (5A) VALUE (1A)
503 IPT_PICKUP Ground Overcurrent (Forward) 0.50 A 0.10 A
504 IPB_PICKUP Ground Overcurrent (Reverse) 0.25 A 0.05 A
505 IPBKFACTOR IPB I1 Restraint 0.0 0.0
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