The application of a current-dependent arc model to arcing at a main distribution panel, a sub-panel and a branch circuit

An arcing fault is a dangerous and unpredictable form of short circuit. Higher arcing-fault current magnitudes are often associated with greater levels of danger. Higher arc currents certainly correlate with greater potential arc-flash hazards and explosions. Within a building system, the largest arcing-fault current is available at the main distribution panel. Since an arcing fault at a sub-panel or in a branch circuit is lower in magnitude and presents less flash-hazard danger, the insidious danger is often overlooked. The magnitude of the arcing-fault current at these locations is often insufficient to immediately trip overcurrent devices, resulting in the escalation of the arcing fault. Despite modern advances in system protection, people are injured or killed each year as a result of arcing faults, initiated through either accidental physical contact or a glow-to-arc transition. The initial phases of this research involved reviewing the arc physics and re-examining the early arc models developed for low-voltage systems and developing better arc models to predict arc current magnitudes in building systems. This paper evaluates the dangers associated with arcing faults at a main distribution panel, a sub-panel, and a branch circuit of a typical building system. Factors determining arc tenacity are addressed.