Specifications

Operations – Short Time Fault Protection
Adjustable Short Time Pickup and Adjustable Short Time Delay
15
800 – 2000A Short Time Pickup for Illustrative Purposes
Adjustable Short Time Pickup
The Short Time Pickup adjustment is used to set the level of
high current the breaker will carry for a short period of time
without tripping.This adjustment, together with the Short Time
Delay, allows downstream breakers time to clear short circuit
faults without tripping the upstream breakers. On trip units for
800, 1200, and 2000A SB breaker sizes, Short Time Pickup
may be set to 1.5, 2, 2.5, 3, 4, 5, 6, 7, 8, or 9 times I
n
. On trip
units for 3200, 4000, and 5000A frame sizes, Short Time
Pickup may be set to 1.5, 2, 2.5, 3, 3.5, 4, 5, 6, 7, or 8 times I
n
.
Short Time Pickup
Adjustable Short Time Delay
The Short Time Delay adjustment is used to set the time
interval the breaker will wait before responding to the current
value selected on the Short Time Pickup adjustment.There are
two modes of operation of this adjustment on all Siemens
Electronic Trip Units; one is a fixed delay, the other is an
inverse I
2
t ramp delay.The I
2
t Delay has the characteristic of
being inversely proportional to the square of the magnitude
of the overcurrent condition.This means that higher overcur-
rent conditions have shorter delays and conversely lower
overcurrent conditions have longer delays.This characteristic
allows for better coordination with downstream circuit break-
ers and fuses. In the fixed delay mode, the Short Time Delay
may be set to 0.07, 0.1, 0.15, 0.2, or 0.3 seconds. In the inverse
I
2
t ramp Short Time Delay mode, the delay may be set to a
calibrated value of 0.07, 0.1, 0.15, 0.2, or 0.3 seconds at a
current equal to 8 times I
n
.
Short Time Delay
Short
Time
Delay
Secs
@8 x l
n
.3
.07
.1
.15
.2
.3
.07
.1
.15
.2
I
2
t
Fixed
l
n
Short
Time
Pickup
8
1.5
2
2.5
3
3.5
4
5
6
7
xl
n
Short
Time
Pickup
8
1.5
2
2.5
3
3.5
4
5
6
7
Available
Switch
Settings
Continuous
Operating
Current
Long
Time
Delay
Short
Time
Pickup
0.1
10,000
1, 0 00
100
10
0.01
0.1
1
110100xl
n
Time In Seconds
.07
.1
.15
.2
.3
Short Time
Fixed Delay
Available Switch
Settings
(All Frame Sizes)
.3
.07
.1
.15
.2
I
2
t
Short Time
l
2
t Delay
Available Switch
Settings
(All Frame Sizes)
0.1
10,000
1, 0 00
100
10
0.01
0.1
1
1
10
100 xl
n
Time In Seconds
0.1
10,000
1, 0 00
100
10
0.01
0.1
1
1
10
100 xl
n
Time In Seconds
Continuous
Operating
Current
Long
Time
Delay
Short
Time
Pickup
Short Time
Fixed Delay
Continuous
Operating
Current
Long
Time
Delay
Short
Time
Pickup
Short Time
l
2
t Delay
800, 1200, 2000A
Frame Sizes
3200, 4000, 5000A
Frame Sizes
9
1.5
2
2.5
3
4
5
6
7
8
Secs@ 8xI
n