V  -    system voltage (kV)
I_bf    -    bolted three phase fault current (kA)
I_a   -    arcing current (kA)
E   -    incident energy (J/cm²)
E_B  - incident energy at boundary distance (J/cm²)
E_n  - normalized incident energy (J/cm²)\
t    -    arcing time (s)
D   - distance from arc to person (mm)
C_B  - distance of boundary from arc point (mm)

Notes:

1. E_B can be set at 5.0 J/cm² for bare skin or at the rating of any proposed PPE.
2. The limit of 5.0 J/cm² is that at which a person is likely to receive second degree burns.
3. To convert J/cm2 to cal/cm2 multiply by 0.239

For a more detailed explanation of the calculation, please see: Arc Flash Calculations Post

Arcing current

System voltages under 1000 V:

Where:
K = -0.153 for open configurations and -0.097 for box configurations

System voltages above 1000 V:

Arcing current is then given by:

Incident Energy

Normalized incident energy:

Where:
K₁ = -0.792 for open configurations and -0.555 for boxed configurations
K₂ = 0 for unground or high resistance ground systems and -0.113 for grounded systems
G  = the conductor gap (see table below)

Incident energy :

- for voltages less than 15 kV

Where:
C_f    = 1.0 for voltages greater than 1000 V and 1.0 for voltages less than 1000 V
x    = is a distance exponent from the table below

- for voltages greater than 15 kV

Flash Protection Boundary

- for voltages less than 15 kV

- for voltages greater than 15 kV

Where:
C_f = 1.0 for voltages greater than 1000 V and 1.0 for voltages less than 1000 V
x = is a distance exponent from the table above