Understanding Electrical Arcs. International Association of Arson Investigators Conference. 1993.

Abstract: This article discusses electrical arcs and why they occur. The IAAI's statistics show that less than 30% of electrical arcing instances result in fires. Electrical arcs are caused by mechanical failure, water penetration, and overloading current. Charts are provided to illustrate the different situations in which an arc will occur. The factors that affect arc resistance include: the medium in which the arc occurs, the sparkover voltage, intermittent or erratic contact, and the ionization of the air. If these factors are combined, the protection devices may fail. Although many arcs are self-clearing, a sustained arc can failure somewhere else in the circuit.

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