Zone-1 Extension; Non-Pilot Operation; 3-Zone Distance Phase And Ground Relay With Reversible Zone-3 Phase And Ground; Inverse Time Overcurrent Ground Backup - ABB REL 301 Instruction Leaflet

I.L. 40-386.4
2.3.4 Zone-1 Extension (Figure 2-8)
This scheme provides a higher speed operation on end zone-faults without the application of a
pilot channel.
If the REL301/302 "SystType" setting is set to "Zone-1 Extension", the zone-1 phase/zone-1
ground (Z1P/Z1G) unit will provide two outputs; one is overreach which is set at 1.25 x Z1 reach
by the microprocessor, and one is the normal Z1 reach. A single shot instantaneous reclosing
device should be used when applying this scheme. The targets Zone-1 Ø/Zone-1G will indicate
either Z1 trip and/or Z1E trip operations. The other functions (e.g., Z2T, Z3T, ac trouble monitor-
ing, overcurrent supervision, unequal-pole closing/ load pickup control, LL trip, etc.) would func-
tion the same as in the basic scheme.
For a remote internal fault, either Z1P or Z1G will detect the fault since they are set to overreach.
High speed trip will be performed via the normal Zone-1 path (Figure 2-5). HST signal operates
the instantaneous reclosing scheme. The breaker recloses and stays closed if the fault has
cleared.
Target Zone-1 Ø and/or Zone-1 G will be displayed. Once the breaker trip circuit carries current,
TRSL operates the 0/5000 timer and satisfies AND 26 for 5000 milliseconds (Figure 2-8). The
output signal of AND 26 will trigger the Zone-1 Ø/Zone-1 G reach circuit, constricting their
reaches back to the normal Zone-1 reaches for 5000 milliseconds. During the reach constricting
periods, if the breaker is reclosed on a Zone-1 permanent fault, it will retrip again. If the breaker
is reclosed on an end-zone zone permanent fault, the normal Z2T time delay trip will take place.
For a remote external fault, either Z1P or Z1G will detect the fault since they are set to overreach.
High speed trip will be performed. HST signal operates the instantaneous 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 Zone-2 back up will take place.
NOTE: The reaches of Z1E are based on the Zone-1 settings multiplied by a factor of
2. 4

NON-PILOT OPERATION

The following features are standard with the REL301/302.
2.4.1

3-Zone Distance Phase and Ground Relay with Reversible Zone-3 Phase and Ground

There are four impedance units per zone: one phase-to-phase unit and three phase-to-ground
units. Zone-3 can be set to forward or reverse for carrier keying or back-up tripping in pilot sys-
tem applications.
2.4.2 Inverse Time Overcurrent Ground Backup (Figure 2-9)
The overcurrent ground backup (GB) unit is to supplement the distance ground protection. It
provides an inverse time characteristic which is similar to the conventional CO characteristics*
(Figures 2-32 through 2-38). The time curves, with a choice of time delay (Reset) or instanta-
neous (Instant) reset characteristic, can be selected by the "GB Type" Setting. The time dial is
set by the "GBT Curve" value. The unit can be selected as directional by using the "GB DIR."
setting and the pickup value is set by "GB Pickup". The directional GB function uses the torque
control approach, as shown. The GB function can be disabled by setting the "GB Type" to "Dis-
abled".
2-6
1.25.