Instantaneous arcing-fault models developed for building system analysis

Abstract

An arcing fault is a dangerous form of short circuit that may have a low current magnitude. In the case of such faults, the magnitude of the current is limited by the resistance of the arc and may also be limited by the impedance of a ground path. This lower level fault current is often insufficient to immediately trip phase overcurrent devices, resulting in the escalation of the arcing fault, increased system damage, tremendous release of energy, and threat to human life. Despite modern advances in system protection and the adoption of National Electrical Code Section 230-95, people continue to be injured or killed from arcing faults, initiated by accidental physical contact or through a glow-to-arc transition. The initial phase of an arcing-fault research project was to review the historical evolution of arc modeling for low-voltage systems. A summary of the electrical aspects and the physics involved in arcing faults appeared in previous work. Today's better analytical tools facilitated the development of new instantaneous arc models with current-dependent arc voltages, which better represent the arcing phenomenon than the assumed arc voltage associated with previous instantaneous arc models. The arc currents in a typical medium-size building system are determined and harmonic analysis is performed.