In a recent InfoPower article (InfoPower Blog (interpower.com), we noted how certain cord-locking mechanisms notched grounding blades on inlets when abruptly disconnected—friction almost certain to create arcing and subsequent carbonized buildup, which may lead to potential fires.
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Arcing & Moisture
Manufactured electrical cord sets containing alloy pins and copper wire are susceptible to arcing for numerous reasons. Pins which are molded too close to each other resulting in air gaps small enough for arcs to jump is one reason. This would also apply to the alloy pins and metal screws on the plug face of rewirable cord sets.
Another reason is moisture. Moisture decreases resistance between circuits which may create an electrical pathway from one circuit to another. This may lead to short-circuiting and subsequent fires and electrical shocks. If you come in contact with an exposed wire or are near an exposed wire when water is present, the electricity (as it follows its grounding path) may pass through your body—Interpower strongly discourages anyone getting near exposed electrical wires in the presence of water or moisture.
Moisture finding its way into electrical wires or near connections may cause corrosion, which increases the potential for arcing. Moisture seeping into cables through applicational misuse, damaged jackets, or the wicking action of paper separators or fillers may permeate wire insulation reducing its resistance and insulation potential—this may cause arcing between conductors or at terminal points. Interpower always recommends utilizing moisture-resistant devices in wet areas and regularly inspecting plugs, connectors, and cables (in any application) for damage where moisture is likely to be present as to prevent failures and accidents.
Gaps & Tracking
Over time, carbon buildup and imperfections such as debris, cavities, corrosion, and cracks allow arcs to “track.” Tracking is the flow of electricity along plastic surfaces where the air gaps are too narrow to extinguish the arc. Depending on your electrical design and other combustible factors, continual tracking may even cause large explosions. Widening air gaps is one solution to extinguish arcs and tracking. Finally, electrical wire that is too tightly crimped can break and cause arcing; and there may be existing gaps along the crimp itself. In truth, the subject of electrical arcing possibilities would likely fill a small library.
Arc Resistance
Arc resistance is measured in the time (seconds) it takes to make an insulating surface conductive under a high voltage/low current arc in controlled environments. Arc resistance in electrical cord sets and components is commonly hipot tested at a higher current than what the product is rated, e.g., a cord set rated at 220V may be hipot tested at or near 320VAC. In other words, arc resistance is the degree to which plastic material resists high voltage arcing and the formation of conductive paths along its surface—the longer it takes (duration of seconds) the less conductive and more resistant your material is to arcing.