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2.2.3
Phase-to-Phase Fault
The phase-to-phase (ØØ) unit (Figure 2-4) responds to all phase-to-phase faults, and
some single-phase-to-ground faults. Equations (5 and 6) are for operating and refer-
ence quantity, respectively. They will produce output when the operating quantity
leads the reference quantity.
(V
- I
AB
(V
- I
CB
2. 3
MEASUREMENT ZONES
REL 301/302 performs line measurement within 3 zones of the transmission line
(Zone1, Zone2, Zone3), and one optional pilot Zone (REL 302). When the REL 302
functional display SystType
function.
When the REL 301/302 trips, the trip contacts will be sealed-in as along as the trip
coil current exists. The trip contact dropout can be delayed (by 50 ms) after the trip
current is removed, providing a jumper (JMP4) is connected on the Microprocessor
module.
2.3.1
Zone1 Trip
For Zone1 phase faults, the Z1Ø unit will identify the fault and operate. The 3Ø fault
logic is supervised by the load restriction logic via AND131C and AND 131 and is also
supervised by the selectable OSB, as shown in Figure 2-5 and 2-18. Output of Z1Ø
satisfies AND-2 and provides a high-speed trip (HST) signal from OR-2 to operate the
trip output telephone relay. The trip circuit is monitored by a seal-in reed relay (S),
which is in-series with each trip contact in the tripping circuits. The S relay will pick
up if the trip current is higher than 0.5 Amp. The operation of the "S" contact will turn-
on the breaker trip indicators (with memory), and feeds back to OR-4 to hold the trip
relay in operation until the breaker trips and 52a contact opens (not shown in
Figure 2-5). The TRSL signal plus the output signal from AND-2 turns on the Zone1
phase trip indicator Zone1Ø. The breaker trip and Zone1 phase trip indicators are
memorized. They can be reset by external RESET voltage or through remote commu-
nication. By pushing the RESET pushbutton, the display will return to the METER
mode, the flashing LED will be reset, but the fault information will still remain in mem-
ory.
The Z1Ø 3Ø trip logic AND-131 is supervised by both the conventional Out-of-Step
block (OSB) and the subsequent OSB logic when the OSB is set to "YES". Z1P logic
AND-2 is also supervised by the Forward Directional Overcurrent Phase (FDOP) unit
for more security on some special power system applications.
Similar operations exist for Zone1 single-phase-to-ground faults. The Zone1G unit
sees the fault and operates; the IoM and FDOG units also operate, satisfying AND-3.
Tripping occurs via OR-2 with Zone1 ground trip indication Zone1G. Logic AND-3 is
also supervised by the signal of "NOT" RDOG (reverse directional overcurrent ground)
"OR" unequal-pole-closing, "OR" LOPB (loss of potential block) for security.
†
Bold type indicates LCD display quality.
(10/94)
Z
)
AB
CP
Z
)
CB
CP
†
is set at "Non Pilot", it will perform the 3-Zone non-pilot
I.L. 40-386.3
(5)
(6)
2-3
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