Читать книгу Arc Flash Hazard Analysis and Mitigation - J. C. Das - Страница 39

Repeat Example 1.1, but for arc in the open air. For high voltage applications, no distinction is made between open and box construction for calculation of arcing current. Therefore, arcing current = 28.578 kA, same as before.

In Equation (1.12), the factor K₁ is −0.792. This gives:

E = 4.184(1)(6.871)(0.5/0.2)(610^0.973/910^0.973) = 48.70 J/cm². This is equal to 11.60 cal/cm².

Also, arc flash boundary reduces to:

This shows a considerable difference between arc in open air and a box.