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I.L. 40-386.4
where V
I
X
Z
I
0
Z
V
2.2.2
Three-Phase Fault
Three-phase (3Ø) fault detection (Figure 2-3) is accomplished by the logic operation of one of
the three ground units, plus the 3Ø fault output signal from the faulted phase selector unit. How-
ever, for a 3-phase fault condition, the distance unit computation will not include zero sequence
compensation. Equations 3 and 4 are for operating and reference quantity, respectively. The unit
will produce output when the operating quantity leads the reference quantity.
V
- I
XG
X
V
Q
where V
I
X
Z
V
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 reference quantity, re-
spectively. They will produce output when the operating quantity leads the reference quantity.
(V
- I
AB
(V
- I
CB
where Z
2. 3
MEASUREMENT ZONES
Both REL301 and 302 perform line protection measurements for 3 zones of the transmission
line (Zone-1, Zone-2, Zone-3), and for one optional pilot zone in REL302. When the REL301 or
302 system type setting "SystType" is set to "Non Pilot", it will perform 3-zone non-pilot pro-
tection.
When REL301 and 302 trip, the trip contacts will be sealed-in as long as the trip coil current ex-
ists. The trip contact dropout can be delayed by 50 milliseconds, after the trip current is re-
moved, by inserting jumper JP4 on the Microprocessor module. See Figure 5-3 for location.
1. Bold type in quotation marks indicates LCD display quantity.
2-2
=
V
, V
XG
AG
BG
=
I
, I
or I
A
B
, Z
=
Positive and zero sequence line impedance in secondary ohms.
L
1L
0
=
1/3(I
+I
A
B
=
Zone reach setting ("Zone1 G", "Zone2 G", "Zone3 G" and "Pilot
CG
1
G")
in secondary ohms for ØG fault
=
Quadrature phase voltages, V
Q
units, respectively.
Z
CP
=
V
, V
XG
AG
BG
=
I
, I
or I
A
B
=
Zone reach setting ("Zone1 Ø", "Zone2 Ø", "Zone3 Ø" and "Pilot
CP
Ø") in secondary ohms for multi-phase faults.
=
Quadrature phase voltages, V
Q
units, respectively.
Z
)
AB
CP
Z
)
CB
CP
=
Zone reach setting ("Zone1 Ø", "Zone2 Ø", "Zone3 Ø" and "Pilot Ø") in
CP
secondary ohms for multi-phase faults.
, or V
CG
C
+I
)
C
, V
CB
, or V
CG
C
CB
and V
for ØA, ØB and ØC
AC
BA
, V
and V
for ØA, ØB and ØC
AC
BA
(3)
(4)
(5)
(6)
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