Dynamic variation characteristics of glowing contact resistance

Glowing contact is one of the ignition heat sources for electrical fires. However, the typical electrical fault has not been paid enough attention in China. Few studies are conducted under 220V(ac), 50Hz and test copper wires complying with China's national standard. In terms of glowing contact, resistance determines the voltage drop, a significant criterion in loose contact detection. Thus, we conduct experiments under 220V(ac) and discuss the dynamic variation characteristics of the glowing contact resistance. The Volt-Ampere characteristics curve shows that the glowing contact oxide bridge is non-linear resistance. Then, we discuss the temporal variation characteristics of the resistance and build up a dynamic model to describe the changes. Results indicate that the growth of the oxide bridge determines the resistance variation trends. Resistance will increase linearly with time when the current is less than 4A. However, the dominant role of oxide length is weakened when currents continue rising. We also explore the effects of wire diameters. It indicates that the difference between various wires is apparent with lower currents. Empirical formulas for calculating the minimum glowing contact resistance under different wire diameters and currents are given. Finally, the current decrease and the decrease ratio can be used as indicators for glowing contact detection.