arcover

An arcover is an unintended electrical arc that bridges between two conductors or from a conductor to ground, usually caused by contamination, moisture, or surface degradation. Unlike a designed spark gap or intentional arcing contact in a switch, an arcover represents a failure mode: electricity finds an unplanned path through air, plasma, or a conductive deposit, often at voltage and current levels the circuit was not built to handle.

Arccovers occur most commonly in high-voltage switchgear, insulators, and circuit boards where spacing between live components is tight. Common triggers include salt spray and industrial dust on ceramic or polymer insulators, moisture bridging a gap after rain or condensation, carbon tracking from previous arcing events, or metallic contamination from corrosion or manufacturing debris. Once an arc initiates, it creates intense localized heat (several thousand Kelvin), which can vaporize material and propagate further damage.

Where arccovers matter

In distribution networks and substations, arccovers on outdoor insulators can trip protective relays and black out circuits. On printed circuit boards in control systems, they may destroy traces or components before fuses respond. The risk is highest in coastal environments, industrial areas with airborne contaminants, and high-altitude locations where air density affects breakdown voltage. Maintenance protocols emphasize cleaning insulators, managing moisture ingress, and applying hydrophobic coatings to reduce creepage paths.

The term "arcover" reflects its nature as coverage of an unintended arc: the arc covers the distance it should not. It differs from flashover, which describes a complete breakdown and conductive path across a surface, though the two terms are sometimes used loosely in the field. Detection relies on thermal imaging, dissolved gas analysis in oil-filled equipment, or simply observing scorch marks and pitting on insulator surfaces.