I.L. 40-385.5
9-4
Curve No.
T
0
K
C
P
R
CO2
111.99
735.00
0.675
1
501
C05
8196.67
13768.94
1.130
1
22705
CO6
784.52
671.01
1.190
1
1475
CO7
524.84
3120.56
0.800
1
2491
CO8
477.84
4122.08
1.270
1
9200
CO9
310.01
2756.06
1.350
1
9342
CO11
110.00
17640.00
0.500
2
8875
CO-5
Long time curve
CO-6
Definite time curve
CO-7
Moderately inverse time curve
CO-8
Inverse time curve
CO-9
Very inverse time curve
CO-11
Extremely inverse time curve
As shown in the setting table, the time curve can be
selected by using the “GBCV” setting, the time dial is
set by the “GTC” value. The following equation can
be used to calculate the trip time for all CO curves
from CO-2 to CO-11:
GBPU = Pickup current setting (0.5 to 4.0A)
GTC = Time curve dial setting (1 to 63)
T
0
, K, C, P and R are constants, and are shown as
below:
The GB function can be set as either directional or
non-directional by setting the “GDIR” to YES or NO.
T
sec
(
)
T
0
K
3
I
0
C
–
(
)
P
---------------------------
+
GTC
24000
---------------for
3
I
0
>
1.5
=
=
T
(sec)
R
3
I
0
1
–
(
)
---------------------
GTC
24000
---------------
for 1
3
I
0
1.5
<
<
=
where
3
I
0
I
F
GBPU
------------------
=
set to DUAL position. However, the GB-unit will be
controlled by the negative sequence voltage and cur-
rent polarized element if the value field is selected to
NSEQ (negative sequence). The pickup value of the
overcurrent unit is controlled by the “GBPU” setting.
The unit can be disabled by selecting the “GBCV” to
OUT.
9.11 ZONE-1 EXTENSION
This scheme provides a higher speed operation on
end zone faults without the application of pilot chan-
nel.
If the MDAR (REL-300) functional display “STYP” is
selected to Z1E, the Z1P/Z1G unit will provide two
outputs. One is overreach (reach to 1.25 times the
zone-1 setting) and one is the normal zone-1 reach.
A single shot instantaneous reclosing device should
be used when applying this scheme. The targets
Z1P/Z1G will indicate either zone-1 trip and/or Z1E
trip operations. The other functions, such as Z2T,
Z3T, ac trouble monitoring, overcurrent supervision,
IT, CIF, unequal-pole closing load pickup control,
load-loss acceleration trip, etc. would remain the
same as in the basic scheme (3ZNP).
For a remote internal fault, (Figure 22), either Z1P or
Z1G will see the fault since they overreach to
The directional GB function uses the torque control
approach as indicated in Figure 21. The directional
element can be selected with either zero sequence
or negative sequence as a polarizing quantity,
depending on the application. By scrolling the func-
tional field to DIRU (directional unit) and selecting
ZSEQ in the value field, the GB-unit will be controlled
by the zero sequence voltage polarized element. The
GB-unit will be controlled by either the zero
sequence voltage 3Vo polarized element and/or the
zero sequence current IP polarized element (current
from a power transformer neutral CT) if the DIRU is
1.25(Z1P/Z1G), high speed trip
will be performed via the normal
Z1T path (Figure 15) AND-2 (or
AND-3) and OR-2. HST signal
operates the instantaneous
reclosing scheme. The breaker
recloses and stays closed if the
fault is automatically cleared.
Target Z1P and/or Z1G will be dis-
played. Once the breaker trip cir-
cuit carries current, it operates the
logic OR-5 (not shown), produces output signal
TRSL, and satisfies logic AND-26 for 5000 ms (Fig-
ure 25). The output signal of AND-26 will trigger the
Z1P/Z1G reach circuit, constricting their reaches
back to the normal Zone-1 for 5000 ms. During the
reach constricting periods, if the breaker is reclosed
on a Zone-1 permanent fault, it will trip again. If the
breaker is reclosed on an end-zone permanent fault,
the normal Z2T will take place.
For a remote external fault, either Z1P or Z1G will see
the fault since they are set to overreach. High speed
