I.L. 40-385.1B
(5/92)
3-7
3.4.12 Instantaneous Forward Directional Over-
current Unit (FDOG)
The instantaneous forward directional overcurrent
ground function (FDOG) is a directional unit depend-
ing on the setting of DIRU as described in the pre-
ceding segment (3.4.11). FDOG is supervised by the
I
om
setting and controls Zone 1, Zone 2 and Zone 3
ground units for security purposes.
3.4.13 Instantaneous Reverse Directional Over-
current Ground Function (RDOG)
Similar to FDOG, the instantaneous reverse direc-
tional overcurrent ground function (RDOG) supervis-
es the ground units to prevent false trip.
3.4.14 Programmable Reclosing Initiation and
Reclose Block
The MDAR system provides the following contact
output for Reclosing Initiation and reclosing block
functions (see Figure 3-19):
• RI1, used for Reclosing Initiation on single pole
trip
• RI2, used for Reclosing Initiation on 3-pole trip
• RB, used for Reclosing Block
The operation of RI1, RI2 and RB contacts is con-
trolled by the setting of the programmable Reclosing
Initiation logic (as shown in Figure 3-19). The opera-
tion of either RI1, RI2, or RB must be confirmed by
the signal of TRSL, which is the trip output of MDAR
operation.
The External Pilot Enable Switch (see Figure 4-1,
TB-5 terminals 9 and 10), is used for enabling the pi-
lot system externally. The PLT setting is similar to
the external pilot enable switch, except it is set from
the front panel (or remotely set via communication
chain).
The most popular Reclosing Initiation practice is to
have Reclosing Initiation on high speed (pilot, Zone
1 and high set) trip only. Programming can be ac-
complished by closing the pilot enable switch and
setting the PLT to YES (see Figure 3-19). AND-84
will produce logic to operate the RI2 relay when re-
ceiving signals from TRSL and AND-89. The pro-
gram is further controlled by the TTYP setting: TTYP
setting OFF: 3PRN provides no output, therefore,
will not operate RI2.
TTYP setting 1PR: 3PRN will provide output “1”
on single-phase-to-ground fault
only and will operate RI2.
TTYP setting 2PR: 3PRN will provide output “1” on
single-phase-to-ground fault or
2-phase faults, and will operate
RI2.
TTYP setting 3PR: 3PRN will provide output “1” on
any type of fault, and will oper-
ate RI2.
The Z1RI, Z2RI and Z3RI settings are provided for
programming on applications where the Reclosing
Initiation on Zone 1, Zone 2 or Zone 3 trip is desired.
Logic AND-62A is controlled by the signal of 3PRN,
therefore, the setting of 1PR, 2PR and 3PR also af-
fect the Z1RI, Z2RI and Z3RI.
In general, the Reclosing Block (RB) relay will oper-
ate on TDT (Time Delay Trip) or OSB (Out-of-Step
Block condition). However, it will be disabled by the
setting of Z1RI, Z2RI, and Z3RI signal.
The RI1 relay is normally used for the single-pole trip
scheme. A Breaker Failure Reclosing Block (BFRB)
feature is available for pilot systems if RB is required
for breaker failure squelch.
3.4.15 Output Contact Test
A “Push-to-Close” feature is included in order to
check all output relay contacts, which include TRIP,
BFI, RI1, RI2, RB, AL1, AL2, GS, Carrier Send and
Carrier Stop. The relay contact check is supplemen-
tary to the self-check because the Microprocessor
self-check routine cannot detect the output hard-
ware. In order to enable the contact test, jumper
(JMP5) on the Microprocessor module must be con-
nected. (See Appendix H, 1.1.13, Step 35 for de-
tailed procedures.)
3.4.16 Sixteen Fault Data
The MDAR system saves the latest sixteen fault
records for all zones. The latest two fault records can
be accessed either via the front panel or via the com-
munication port. Fault records 3 thru 16 can only be
accessed via the communication port. On the front
panel, the “LAST FAULT’ information is of the last
fault, the “PREVIOUS FAULT” information is of the
previous fault. These displays contain target infor-
mation. When targets are available, the LAST
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