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BCS Switchgear Inc.
Arcflash Reduction Maintenance Switch
Application and Installation
1.3 Example Calculation
The following is a calculation example for a 1600 A circuit breaker
with a 1600 A sensor. The time current graph (Figure 2) shows
the circuit breaker settings before and after the Arcflash Reduc-
tion Maintenance Switch installation.
In this example, the following power system conditions exist:
Bolted fault current through the reductive
device to fault location
Arcing fault current calculated using
TM
IEEE Std. 1584
-2002
85% of arcing fault current per
TM
IEEE Std. 1584
-2002
Running load current through circuit breaker
Transient motor in-rush current through breaker
(6 × 1.6 × 480 A)
Total running load + transient motor in-rush load =
Table 2. Example Calculations for All RS Positions.
REDUCTION
BUS
SETTING
kV
INACTIVE
0.48
[R5]
0.48
[R4]
0.48
[R3]
0.48
[R2]
0.48
[R1]
0.48
Note:
* Arcing current low tolerances (85%) used.
IL01906001E
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= 40.00 kA
= 19.98 kA
= 16.98 kA
=
1.12 kA
=
4.80 kA
5.92 kA
REDUCTIVE
REDUCTIVE
DEV.
DEV.
BOLTED
ARCING
FAULT
FAULT
kA
kA
40.00
19.98
40.00
19.98
40.00
19.98
40.00
19.98
40.00
19.98
40.00
16.98
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Setting choices for the RS are: 2.5 ×, 4.0 ×, 5.9 ×, 7.6 × or
9.8 × rating plug value with a pickup tolerance of
1. Setting 9.8 × 1600 A =15.68 kA± 10% =pickup range of
14.11 to 17.25 kA.
2. Setting 7.6 × 1600 A =12.16 kA± 10% =pickup range of
10.94 to 13.38 kA.
3. Setting 5.9 × 1600 A =9.44 kA ± 10% =pickup range of
8.50 to 10.38 kA.
4. Setting 4.0 × 1600 A =6.40 kA ± 10% =pickup range of
5.76 to 7.04 kA.
5. Setting 2.5 × 1600 A =4.00 kA ± 10% =pickup range of
3.60 to 4.40 kA.
In this example, there are two appropriate setting choices (either
5.9 [R3] × or 7.6 [R2] ×). Either of these settings are above the
total plus transient load (5.92 kA) and below the minimum arcing
current (16.98 kA). Either of these settings reduces the incident
energy from 10.7 to 2.2 cal/cm
TRIP /
ARCFLASH
DELAY
BOUNDARY
TIME
in. (mm)
sec
0.24
106 (2692)
0.05
37 (940)
0.05
37 (940)
0.05
37 (940)
0.05
37 (940)
0.24
94 (2388)
Instructional Literature
Effective: May 2005
2
(refer to the Table 2).
WORKING
INCIDENT
DISTANCE
ENERGY
2
in. (mm)
cal/cm
24 (610)
10.7
24 (610)
2.23
24 (610)
2.23
24 (610)
2.23
24 (610)
2.23
24 (610)
8.97
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Page 3
±
10%.
NFPA70E
PPE
CLASS
Class 3
Class 1
Class 1
Class 1
Class 1
Class 3*
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