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I.L. 40-386.3
Z1 reach by the microprocessor, and one is the normal Z1 reach. A single shot instan-
taneous reclosing device should be used when applying this scheme. The targets
Zone1Ø/Zone1G will indicate either Z1 trip and/or Z1E trip operations. The other
functions (e.g., Z2T, Z3T, ac trouble monitoring, overcurrent supervision, Inst., CIF
Trip (CIF), unequal-pole closing load pickup control, LL trip, etc.) would remain the
same as in the basic scheme.
For a remote internal fault (refer to Figure 2-8), either Zone1Ø or Zone1G will see the
fault since they are set to overreach. High speed trip will be performed via the normal
Z1 path (Figure 2-5), i.e., AND-2 (or AND-3), OR-2. HST signal operates the instanta-
neous reclosing scheme. The breaker recloses and stays closed if the fault is automat-
ically cleared.
Target Zone1Ø and/or Zone1G will be displayed. Once the breaker trip circuit carries
current, it operates the logic OR-5 (not shown), produces output signal TRSL, and sat-
isfies logic AND-26 for 5000 ms (Figure 2-8). The output signal of AND-26 will trigger
the Zone1Ø/Zone1G reach circuit, constricting their reaches back to the normal
Zone1 for 5000 ms. During the reach constricting periods, if the breaker is reclosed
on a Zone1 permanent fault, it will retrip again. If the breaker is reclosed on an end-
Zone permanent fault, the normal Z2T will take place.
For a remote external fault, either Zone1Ø or Zone1G will see the fault since they are
set to overreach. High speed trip will be performed. HST signal operates the instanta-
neous reclosing scheme. The breaker recloses and stays closed if the fault has been
isolated by the adjacent line breaker. However, if the adjacent line breaker fails to trip,
the normal remote back up will take place.
NOTE:
2. 4
NON-PILOT OPERATION
The following features are standard with the REL 301/302
2.4.1
3-Zone Distance Phase and Ground Relay with Reversible Zone3 Phase and Ground
There are four impedance units per zone: one phase-to-phase unit and three phase-
to-ground units. Zone3 can be set to forward or reverse for carrier keying or back-up
tripping in pilot system applications.
2.4.2
Inverse Time Overcurrent Ground Backup
The overcurrent ground backup (GB) unit is to supplement the distance ground pro-
tection. It provides an inverse time characteristic which is similar to the conventional
CO characteristics (Figure 2-32 thru 2-38). The time curves can be selected by the GB
Type (GBCV) Setting. The time dial is set by the GBT Curve (GTC) value. The unit can
be selected as directional by using the GB DIR (GDIR) setting and the pickup value is
set by GB Pickup (GBPU). The directional GB function uses the torque control ap-
proach, as indicated in Figure 2-9. The GB function can be disabled by setting the GB
Type (GBCV) to the OUT position.
The directional unit is determined by the setting of "Dir Type (DIRU)" which can be set
to Zero Sequence (ZSEQ) (zero sequence voltage), Dual Polariz (DUAL) (zero sequence
2-6
The reaches of Z1E are based on the Zone1 settings multiplied by a fac-
tor of 1.25.
(10/94)
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