ABB MDAR Instruction Manual page 35

TDT signal can be connected to the reclosing block
logic.
Either or both Zone-2 phase and Zone-2 ground
function(s) can be disabled by selecting the Z2P and/
or Z2G to OUT; or can be disabled by selecting the
T2P and/or T2G to BLK.
9.6 ZONE-2 TRIP
For Zone-3 phase faults, the Z3P unit (forward or
reverse looking, depending on the Z3FR set to FWD
or REV) will see the faults and operate the Zone-3
phase timer T3P. The Z3P output plus the T3P timer
output satisfy AND-6 as shown in Figure 17. AND-6
output provides time delay trip signal TDT via OR-3.
Signal TDT picks up OR-4 (Figure 15) and operates
the trip relay. The tripping and targeting are similar to
Zone-1 trip, except with zone-3 phase time delay trip
Z3P indication.
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Zone-3 3 unit is not supervised by the OSB logic.
For Zone-3 single-phase-to-ground faults, the Z3G
sees the fault and operates. This plus the operation
of the I , satisfy AND-7. This provides the TDT sig-
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nal, then trips via OR-3 with zone-3 ground time
delay trip indicator Z3G. TDT signal can be con-
nected to the reclosing block logic. For security, the
Z3G unit is also supervised by the signal of RDOG
when it is set for reverse looking (or by the signal of
FDOG when it is set for forward looking) via logic
OR-171B and AND-171A as shown in Figure 17.
Either or both Zone-3 phase and Zone-3 ground
function(s) can be disabled by selecting the Z3P and/
or Z3G to OUT; or by selecting the T3P and/or T3G
to BLK.
9.7 DIRECTIONAL INSTANTANEOUS
OVERCURRENT TRIPS
The directional instantaneous overcurrent units IAH,
IBH, ICH and IOH are supervised by the FDOP (A, B
and C) for phases and by FDOG for ground. These
units are normally set high to detect those faults
which occur in the Zone-1 area. Therefore, their trip-
ping will occur via OR-2 for HST, as shown in Figure
18. The use of directional supervision will minimize
some setting difficulties in applications. The setting of
LOPB has no effect to the high-set trip function
except the units will become a non-directional during
LOP condition if the LOPB setting is set to YES.
These high-set trip functions can be disabled by set-
ting the ITP (phase) and/or ITG (ground) to OUT.
9.8 CLOSE-INTO-FAULT TRIP
In order to supplement distance unit operation when
the circuit breaker is closed into a fault and line side
potential is used. The CIF close-into-fault trip circuit,
as shown in Figure 19, includes logic AND-22, OR-3
and 100/180 ms and 16/0 ms timers. Logic AND-22
is satisfied and produces a trip signal for 180 ms after
circuit breaker closing (52b contact opened) if the
overcurrent unit(s), I , I
AL
11, and if any phase voltage is below the preset level
of the LV-units (OR-222A). Tripping will be via OR-3,
with RB and CIF target.
The application of the "close-into-fault" function is
selected by the setting of the CIF to YES.
9.9 UNEQUAL-POLE CLOSING LOAD PICKUP
CONTROL
The ground units may pick up on a condition of load
pickup with unequal breaker pole closing. The high
speed trip ground units Z1G and FDOG/I
be supervised under this condition. This can be
achieved, as shown in Figure 20, by inserting a 0/50
ms timer and controlling by the 52b signal to super-
vise the Z1G trip path AND-3 (Figure 15) and FDOG/
I trip path AND-188 (Figures 26 and 34). It should
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be noted that the 50 ms time delay will have no effect
on a normal fault clearing.
The ground distance unit PLTG is less sensitive as
the FDOG, it is not need to have this supervising cir-
cuit.
On internal ground faults, if the mechanical actuator
of the circuit breaker operates, but the arc does not
extinguish (e.g. due to low gas pressure), the closing
action of the 52b contact, connected to MDAR (REL-
300), will reset the Z1G trip path AND-3, and ulti-
mately, the BFI contact. This may introduce interrup-
tion to the BF scheme if BFI logic does not provide
seal-in circuit. The AND-3C logic in Figure 20 will
solve this problem.
9.10 INVERSE TIME DIRECTIONAL OR NON-
DIRECTIONAL OVERCURRENT GROUND
BACKUP (GB)
The overcurrent ground backup unit GB is to supple-
ment the distance ground protection on high resis-
tance ground faults. Its selectable time characteristic
curves, as shown below, are similar to the conven-
tional CO relays.
CO-2 Short time curve
I.L. 40-385.5
, I or I , operate OR-
BL CL OM
should
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9-3