Measurement of arc energy during insulation ignition

A digital arc energy meter was developed for insulation-ignition measurements. The meter takes 54 discrete samples of the current through, and voltage across, the electrodes during each 60-Hz cycle. It multiplies the values, sums the products, multiplies the sum of products by the sampling time (time between samples), and displays the result in Joules. The computation is accurate to 3%. The device is designed to handle arcs that last up to 300 ms, although the typical high-energy arc lasts approximately 75 ms. Tests were run on various NEMA-grade materials. It is concluded that the most satisfying result of the investigation is the consistency in the graphs of arc energies. In spite of the variation from cycle to cycle within the test, these graphs show that each grade of material has a detectable signature.<>