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SKM Power*Tools for Windows
Standard allows the choice of NFPA 70E, IEEE 1584, or NESC 2007 methods. If NFPA
70E method is selected, the equations published in NFPA 70E – 2004 Annex D.6 will be
used to calculate the incident energy and flash boundary. If the IEEE 1584 method is
selected, the equations published in the IEEE 1584 2002 and NFPA 70E – 2004 Annex D.8
will be used to calculate the arcing fault current, incident energy, and flash boundary. The
IEEE 1584 method is based on more recent and expanded test data, and is the preferred
method. Since IEEE 1584 method is also part of the NFPA 70E 2004, using the IEEE 1584
method could be considered as comply with NFPA 70E as well. If NESC 2007 method is
selected, the tables from NESC 2007 are used to calculate the incident energy and
minimum approach distance.
Flash Boundary Calculation Adjustments - The Flash Boundary is normally calculated
by setting the incident energy to 1.2 cal/cm^2 and use the incident energy equation to
reverse calculate the flash boundary. An option to use 1.5 cal/cm^2 for equipments above
1 kV and trip time < 0.1 seconds is provided here. This is recommended by NFPA 70E –
2004 (section 130.3 (a) page 70E-25).
Equipment Below 240 Volts Options:
Two separate list boxes are provided due to the difference in applicable voltage criteria to
the location of the arcing fault in addition to Bolted Fault magnitude or upstream
Transformer Size presented in IEEE 1584 and NFPA 70E standards.
- The first list box represents the Equipment Voltage range and the choices are "<=
240 V" (equal to 240 V or below) referred to NFPA 70E Std Table
130.7.(C)(9)(a), or "< 240 V" ( less than 240 V) referred to IEEE 1584-2002 Std.
- The second list box provides the following options:
- Option1: Report as Category 0 if Bolted Fault < 10 kA. Referred to Note 3
in Table 130.7.(C)(9)(a) of NFPA 70E-2004 Std.
- Option2: Report as Category 0 if Transformer Size < 125 kVA. Referred to
IEEE 1584-2002 Std.
- Option3: Report as Category 0 if Bolted Fault < 10 kA or Transformer Size < 125
kVA.
- Option4: Report as Category 0 if Bolted Fault < 10 kA and Transformer Size <
125 kVA.
- Option5: Report Calculated Values From Equations. Use normal incident energy
calculation methodology.
If option 1, 2, 3, or 4 is selected, and the calculated incident energy is smaller than 1.2
cal/cm^2, the calculated value will be reported and used to calculate the flash
boundary. If the calculated incident energy is greater than 1.2 cal/cm^2, it will be
reported as 1.2 cal/cm^2.
