Hello Peter, I notice that you have written to me personally as well as posting 2 threads on this forum without reply. Iâ€™ll do my best to address your question on this forum in the hope that more learned forum members will set out to correct me if I get it wrong or add to my reply.

The K factors arise out of the fact that the equations are based upon the least squares method of obtaining the best fit to test data which was obtained in large power laboratories. (The least squares method can be described as a method of fitting data to a formula through regression analysis.) As you can appreciate, predicting electrical arcs is not an exact science particularly at low voltages. The K factors are actually used in the equation for predicting arcing current below 1000 volts and if you are preparing a thesis which is specifically about IEEE 1584 then you will be interested to know that there are imperfections with the formulae. You will do well to read a couple of articles that are linked below.

The first one was referred to me by WDeanN on this forum after I stumbled across one anomaly some time ago where I calculated a higher arcing current than the bolted figure which is impossible in real life but is possible using the equations.

http://www.arcflashforum.com/showthread.php?t=74&highlight=mike+frain
The other article is available through the Easypower.com website called â€œPractical Solution Guide to Arc Flash Hazardsâ€, written by Chet Davis, PE, Satish Shrestha, Conrad St. Pierre, and Robert Luo, Ph.D. This has a section on variation of arcing current.

The 0.2 seconds arc duration and the 600mm working distance are simply the parameters that are use in the above tests. Why these exact parameters were chosen is something that I canâ€™t help you with but there may be somebody in the know.

I wish you well in your work, Mike