Help to interpret Arcpro results(and IEEE1584) for practicle use:
-I am use to calculate with IEEE1584 then I get a incident energy value and a PPE class.:
1.When I look at clothing they have a ATPV value for instance 12 cal/cm2. Can this be directly compared with the incident energy value?
2. When I calculate with arcpro I get both heat energy(Cal/cm2) and Heat flux(cal/s/cm2). How can I use this to compare with ATPV on clothing?

Anyone?

The goal is for the Arc Rating of the protective clothing and equipment should be sufficient for the incident energy. The catch is this: The results of an incident energy calculation are based on a specific distance known as the working distance. Typically this might be 18, 24 or 36 inches. If a person is wearing PPE based on the calculated value and distance, but then gets closer than the distance used, the incident energy increases exponentially. NFPA 70E addresses this by stating that "additional PPE shall be used for any parts of the body closer than the working distance at which the incident energy was determined." Also keep in mind injuries can still occur - it's not a guarantee.

It's a good question indeed. A PPE rated to withstand 12 cal/cm2 delivered within 1 sec (heat flux of 12 cal/cm2/sec) may burnout when the energy is delivered within shorted time interval but at higher heat flux. As an example, 100% denim will take 12 cal/cm2 delivered in one second before setting on fire, while take only 9 cal/cm2 when the energy is delivered with 120 cal/cm2/sec heat flux. The example is based on information published in Ian Hymes, Warren Boydell, 1996, Thermal Radiation: Physiological and Pathological Effects (Belinda Prescott). Check also Behavior of apparel fabrics during convective and radiant heating for more information. Unfortunately, the impact of heat flux on threshold incident energy to 2nd degree burn as well as threshold incident energy for ignition or melting of fabrics is very well know but widely ignored and denied in modern day arc flash hazard analysis standards.