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Arc flash Hazard Analysis

Simple method for Arc Flash hazard Analysis per 2018 NFPA 70B






The following is an example of identifying the arc flash hazard per 130.5(E) for the arc flash boundary (AFB) and 130.5(G) using the incident energy analysis method. 

Various information about the system may be needed to complete this analysis, but two values are absolutely necessary: 

1. The available 3 Ø bolted fault current 

2. The fuse type/amp rating Consider the one-line diagram in Figure 3.1.5.3.a and then follow the examples that take the steps needed to conduct an arc flash hazard analysis

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The following information utilizes the simplified fuse formulas based upon IEEE 1584-2002 Guide for Arc Flash Hazard Analysis and shown in 2018 NFPA 70E Annex D.4.6 and shows the steps necessary to conduct an arc flash hazard analysis when using Low-Peak fuses and Table 3.1.5.3.b: arc flash incident energy.

 1. Determine the available bolted fault current on the lineside terminals of the equipment that will be worked on. 

2. Identify the amp rating of the upstream Low-Peak fuse that’s protecting the panel where work is to be performed. 

3. Consult Table 3.1.5.3.b to determine the Incident Energy Exposure (I.E.) level. 

4. Determine the AFB that will require personal protective equipment (PPE) based upon the incident energy. This is simplified by using the column for AFB in Table 3.1.5.3.b. 

5. Identify the minimum requirements for PPE when work is to be performed inside of the AFB by consulting the requirements found in NFPA 70E Table 130.5(G). 600 V, 3Ø MLO panel 42 kA available bolted fault current LPS-RK-600SP 600 A, Class RK1 fuses 

• Incident energy 0.25 cal/cm2 @18” 

• 6” AFB Example 1: Arc flash hazard analysis using Bussmann series current-limiting fuses (notes referenced appear on page 3-28) 

The following is a simple method when using certain Bussmann series fuses; this method is based on actual data from arcing fault tests (and resulting simplified formulas shown in NFPA 70E Annex D.4.6 and 2002 IEEE 1584) with Bussmann series current-limiting fuses. Using this simple method, the first thing that must be done is to determine the incident energy exposure level . 

This  process  has been when using LPS-RK, LPJ, TCF, LP-CC or KRP-C Low-Peak fuses, or JJN or JJS Limitron fuses and FCF fuses. In some cases the results are conservative.


Example 1: Arc flash hazard analysis using Bussmann series 
current-limiting fuses 

The following is a simple method when using certain Bussmann series  fuses; this method is based on actual data from arcing fault tests (and resulting simplified formulas shown in NFPA 70E Annex D.4.6 and 2002 IEEE 1584) with Bussmann series current-limiting fuses. Using  this simple method, the first thing that must be done is to determine 
the incident energy exposure level . We have simplified this process  when using LPS-RK, LPJ, TCF, LP-CC or KRP-C Low-Peak fuses, or JJN  or JJS Limitron fuses and FCF fuses. In some cases the results are conservative

In this example, the lineside OCPD  is an LPS-RK- 600SP, Low-Peak current-limiting fuse. Simply take the available 3 Ø  bolted fault current at the panel — in this case 42 kA — and locate it on  the vertical column in Table 4. Then proceed directly to the right to the 
401-600 A fuse column and identify the I.E. (incident energy) and AFB.

With 42 kA of 3 Ø bolted available fault current, the table shows that 
when relying on the LPS-RK-600SP Low-Peak fuse to interrupt an arcing 
fault, the incident energy is 0.25 cal/cm2. Notice the variables required 
are the available 3 Ø bolted fault current and the Low-Peak current-
limiting fuse amp rating.

The next step in this simplified arc flash hazard analysis is to determine 
the AFB. With an incident energy of 0.25 cal/cm2 and using the same 
table, the AFB is approximately 6 inches, which is found next to the 
incident energy value previously located.

 This AFB distance means that anytime work is to be performed inside of this distance, 
including voltage testing to verify that the panel is de-energized, the  worker must be equipped with the appropriate PPE.

The last step in the arc flash hazard analysis is to determine the  appropriate PPE for the task. To select the proper PPE, utilize the  incident energy exposure values and the requirements from NFPA 70E.  NFPA 70E Table 130.5(G) has requirements for the PPE based upon the  incident energy exposure level. NFPA 70E Annex H is a resource for 
guidance in selecting PPE; 

When selecting PPE for a given application or task, keep in mind that  these requirements from NFPA 70E are minimum requirements. Having  additional PPE, above what is required, can further assist in minimizing  the effects of an arc flash incident. Another thing to keep in mind is that  PPE available on the market today does not protect a person from the  pressures, shrapnel and toxic gases that can result from an arc-blast,  which are referred to as “physical trauma” in NFPA 70E. Existing PPE is only tested to minimize the potential for burns from the arc flash. 

Arc flash incident energy levels based upon 1-600 A Low-Peak LPS-RK and 601-2000 A Low-Peak KRP-C fuses


Incident Energy (I.E.) values expressed in cal/cm2, Arc Flash Boundary (AFB) expressed in inches.





This article has been extracted from the Selecting protective Devices Handbook by Bussmann



Download the free Handbook here


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