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Op erations -Instantaneous Fault Protection
Adjustable Instantaneous Pickup
4
5
Instantaneous
Pickup
xl,
10
9
Adjustable Instantaneous Pickup
The Instantaneous Pickup adjustment is used to set the
current level at which the breaker will trip without an
intentional time delay. Non-delayed tripping, as a result of
a severe overcurrent condition, minimizes potential dam
age to electrical systems and equipment. On Siemens
Electronic Trip Units, the Instantaneous Pickup adjust
ment may be set to 1.5, 2, 3, 4, 5, 6, 7, 8, 9, or 10 times I,
1000
en
1 00
'0
c
�
0
0
<D
<D
1 0
E
f'=
t?J 4
5
6
2
7
.::: ::'
1.5
8
<I
9
10
Instantaneous Pickup
xlr
1 0
1 00
Available Switch Settings
Instantaneous Override
On all trip units, an instantaneous override function has
been provided. It is set nominally at the short time rating of
the respective breaker frame size. This allows the breaker
to ride through high faults up to its short time capability;
however, it is self-protecting above these values.
Breaker
Frame Size
800A
2000A
4000A
(Making Current Release)
Discriminator Circuit
This circuit overrides the short time delay function should
the breaker attempt to close into a faulted system, tripping
the breaker instantaneously. The discriminator function is
enabled for the first 6 cycles of current flow, after which
normal short time characteristics operate.
1 000
en
1 00
'0
c
0
�
0
<D
1 0
<D
E
F
. 1
Instantaneous Override (Illustrated with Short Time Fixed Delay)
Short Time kA Rating
(.500 seconds max.)
25
35
65
xl r
1 0
1 00
31
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