RF Current Produced from Electrical Arcing

The RF current produced by an air arc in a 480 Vac line-line system was investigated for arcing currents in the range of 5A_rms to 100A_rms. Time resolved frequency maps, obtained using a real-time spectrum analyzer (RSA), were used to show how polarity and electrode material affected the measured RF intensity. In addition to the experimental data, a model was created to support a new theory explaining the origins of the RF current. This proposed theory takes into consideration the electrode surface geometry, cathode spot current density, and spot motion/stability properties to develop an electrical model of the arc. The model was used to illustrate how the RF current intensity changes with arc current magnitude. This work is useful to those who want to gain an understanding of RF currents generated in arcs, especially for those developing arc fault sensing devices.