ETAP FAQ # 15
 

What is the comparison of NFPA 70E-2000 an IEEE 1584-2002 standards
for Arc Flash Analysis?
 
Description: Arc Flash Analysis calculates the potential arc flash hazard distance and incident energy to which workers could be exposed to while working on or near electrical equipment.
   
Version: ETAP 4.7.4
   
Published: June 11, 2003
 

The ETAP Arc Flash Analysis module estimates the arc flash incident energy under a bolted three-phase short circuit fault and determines the flash protective boundary to live parts for shock protection. The flash protection boundary is the distance a worker not wearing flame-resistant personal protective equipment (PPE) must stay away from a job site involving a possible hazardous arc flash. The arc flash analysis is conducted in conjunction with the ANSI/IEEE and IEC Device Duty calculations.

There are two industry standards relating to Arc Flash:

  • National Fire Protection Agency (NFPA) 70E-2000
  • IEEE 1584-2002

The ETAP Arc Flash Analysis has the following program features:

  • Automatically report a table of arc flash analysis for every faulted bus


  • Automatically computes bolted short circuit current for every faulted bus


  • Determines the flash protection boundary as a function of arc duration for enclosed and open box configurations


  • Determines incident energy exposure (cal/cm2) as a function of distance


  • Determines incident energy exposure (cal/cm2) as a function of arc location


  • Determines incident energy exposure (cal/cm2) in open air


  • Determines incident energy exposure (cal/cm2) in a cubic box
 
Comparison of NFPA 70E-2000 and IEEE 1584-2002 Standards
 
 
NFPA 70E-2000
IEEE 1584-2002
     
Unit of Measure
Calories/cm2
Calories/cm2
   
Voltage Range
208 V - 600 V
208 V - 600 V (Empirical)
   
Voltage Range
15 kV+ (Lee Method)
   
Current Range
16 kA - 50 kA
0.7 kA - 106 kA
   
Arc Duration Range
1/4 Cycle - 120 Cycles
1/4 Cycle - 120 Cycles
   
Installations
Open Air, Cubic Box
Open Air, Cubic Box
   
Arc Distance
18" - 48"
18" - 48"
 
Summary of a Results Comparison Between NFPA 70E-2000 and IEEE 1584-2002 Standards
 
Calculations using the NFPA 70E-2000 and IEEE 1584-2002 standards were done on the same system. The system contained buses at voltage levels varying from 208 volts to 35,000 volts. Based upon the above table, the NFPA standard is designed to specifically handle 208-600 volts and 16-50 kAsc. Therefore, values shown in the 208 V case, 4.16 kV case, and 35 kV case are all extrapolated results for NFPA 70E-2000.
 
Summary Table
 
   
NFPA 70E-2000
IEEE 1584-2002
       
208 V, 18"
Open Air, 12.96 kAsc
Conservative
Non-Conservative
208 V, 18" Cubic Box, 12.96 kAsc Conservative Non-Conservative
       
480 V, 18"
Open Air, 28.99 kAsc
Similar
Similar
480 V, 18"
Cubic Box, 28.99 kAsc
Non-Conservative
Conservative
600 V, 18"
Open Air, 19.50 kAsc
Non-Conservative
Conservative
600 V, 18"
Cubic Box, 19.50 kAsc
Non-Conservative
Conservative
4.16 kV, 18"
Open Air, 27.71 kAsc
Non-Conservative
Conservative
4.16 kV, 18"
Cubic Box, 27.71 kAsc
Non-Conservative
Conservative
For 15 kV and above, the results for open air and cubic box calculations are similar, therefore, we are displaying only the open air values during this comparison.
       
35 kV, 18"
28.01 kAsc
Non-Conservative
Conservative
 

Several trends are displayed via the results of the calculation.

Regardless of the standard selected, the incident energy exposure increases as a function of increased voltage, and decreases as a function of increased distance from the source.

The variation in results due to an enclosure (cubic box) is most severe at lower voltages. As the voltage levels increase, the results become similar. Mathematically, above 15 kV, the formulae become so similar that only the open air results are displayed.

At a fixed distance of 18", NFPA is conservative at lower voltage levels, and becomes less conservative as voltage is increased. The cross-over point between NFPA and IEEE is seen in the test case at 480 volts in open air. IEEE results become conservative at the higher voltage levels.
 
Plots

208 V Open Air
Incident Energy Exposure as a Function of Time for an Arc in Open Air at 208 Volts and a Distance of 18 Inches
 
 
208 V Cubic Box
Incident Energy Exposure as a Function of Time for an Arc in Closed Box at 208 Volts and a Distance of 18 Inches
 
 
480 V Open Air
Incident Energy Exposure as a Function of Time for an Arc in Open Air at 480 Volts and a Distance of 18 Inches
 
 
480 V Cubic Box
Incident Energy Exposure as a Function of Time for an Arc in Closed Box at 480 Volts and a Distance of 18 Inches
 
 

600 V Open Air
Incident Energy Exposure as a Function of Time for an Arc in Open Air at 600 Volts and a Distance of 18 Inches
 
 
600 V Cubic Box
Incident Energy Exposure as a Function of Time for an Arc in Closed Box at 600 Volts and a Distance of 18 Inches
 
 
4.16 kV Open Air
Incident Energy Exposure as a Function of Time for an Arc in Open Air at 4160 Volts and a Distance of 18 Inches
 
 
4.16 kV Cubic Box
Incident Energy Exposure as a Function of Time for an Arc in Closed Box at 4,160 Volts and a Distance of 18 Inches
 
 
35 kV
Incident Energy Exposure as a Function of Time for an Arc in Open Air at 35 kV and a Distance of 18 Inches
For voltage levels above 15,000 Volts the theoretically derived Lee Method is used by IEEE 1584-2002,
t he incident energy exposure equations used for the NFPA 70E are only valid below 600 Volts.
The values shown below are well outside the allowable range.

 
Data
 

Arc Flash Analysis NFPA 70E-2000
(PDF 49 KB)

Arc Flash Analysis IEEE 1584-2002
(PDF 49 KB)
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