2011 NEC Section 690.11 requires detection and interruption of “arcing faults resulting from a failure in the intended continuity of a conductor, connection, module, or other system component.” This requirementdescribes what are commonly called “series” arc-faults and does not include “parallel” arc-faults resulting from a failure in insulation between two conductors.
How are Arc-Faults Formed?
In a series arc-fault a conductor is interrupted, creating a gap in the conductive path while current is flowing. This creates a spark that ionizes the surrounding air, producing plasma. If the current is sufficiently high,enough plasma is created to keep the current flowing across the gap in the conductive path. The current is now conducted via the plasma and is visible as an electric arc.