Joule Heating and Arc-Fault-Induced Electrical Fires for Commercial-Grade Copper and Brass in Low-Voltage Electrical Systems

Abstract

Electrical fires are usually caused by contact heating, for which the mechanism of heat accumulation is currently not well understood. Previous studies done by many researchers were able to recognize the pattern of the electrical waveform, but the actual mechanism behind such phenomenon is still a mystery. This research focuses on electrical plugs and sockets made from copper and electrical brass, which are the main components where unsupervised electrical fires often occur due to mechanical wear and electrical breakdown. We performed experiments using commercial-grade replacement electrical sockets and plugs made primarily to be compliant with Japan Industrial Standards. Oxides of the materials were formed by subjecting the samples to variable amounts of current and repeatedly making and breaking contact to create an electrical discharge. The copper(I) oxide that formed due to electrical discharge was found to have intrinsic semiconductor properties that played a critical role in electrical fires involving copper components. Poor contacts exhibited distinct behavior, such as contact vibration which also exacerbated the deterioration. From these findings, we concluded that any contact surface made of copper or a copper alloy may have a greater risk of starting an electrical fire than other types of material when a certain arcing condition is met.

Keywords

• arc fault
• copper oxide
• glowing connection
• Joule heating
• vibration