Electrical arcing is when electrical current jumps a gap in a circuit or between two electrodes (conductors of electricity). You may be familiar with this activity from the classic science experiment – Jacob’s Ladder. However, arcing can produce an arc flash where the electricity flows or discharges along an unintended path. These flashes ignite with particulates in the environment, which can be anything from dust to gas. The arcs can exceed over 10,000 °F and electrical fires are the likely outcome of these arc flashes.
Arcing in Electrical Panels
Arc flashes can happen anywhere there is electrical current flowing. Thirty-six percent of arc flashes occur in electrical panels and enclosures. Electrical panels contain many different circuits, buses, and connections. Arcing usually occurs when a circuit becomes overloaded and overheats. The overheating causes damage not only to the circuit breaker but also to its connection to the bus. Once damaged, a circuit breaker can malfunction and continue to let electricity flow between its connection instead of tripping. A circuit breaker is designed to trip or break the circuit connection and not function until it is reset. However, if a damaged circuit breaker continues to allow electricity to flow, arcing becomes a possibility.
Other Causes of Arcing
Wiring in an electrical panel can get damaged even when it is enclosed and guarded against potential hazards. Possible causes include:
- Wiring that is severed or disconnected during routine maintenance or new installations
- Insulation covering the wire gets damaged and exposed
- The electrical cabinet is left open or damaged leaving it susceptible to the elements
- Over-fusing which is when too many fuses are placed inside of an electrical panel
- Faulty equipment or components
How Arcs Cause Fire
According to the National Fire Protection Association - NFPA 921 Section 14.9.1, for ignition to be from an electrical source, the following must occur:
- Electrical wiring, equipment, or component must have been energized from a building's wiring, an emergency system, a battery, or some other source.
- Sufficient heat and temperature to ignite a close combustible material must have been produced by electrical energy at the point of origin by the electrical source.
As stated above, arc flashes produce temperatures that can exceed 10,000°F. This heat is well above the melting point of the wire insulation, which is typically 194°F. Arc flash fires commonly start with the burning of the wire insulation (plastic covering), but can also be fueled from dust particles and other contaminants within the environment.
Arc Flash Prevention
Within your electrical panel, you can install Arc Fault Circuit Interrupters instead of a standard circuit breaker. AFCIs are designed to detect a wide range of arcing electrical faults. They detect these faults by using advanced electronic technology to monitor the circuit for the presence of “normal” and “dangerous” arcing conditions. One downside of AFCIs is the price. AFCIs typically costs $30-$40 each while a normal circuit breaker costs $2-$5 each. Much debate is out there on whether they actually work because arcing still happens when AFCIs are installed, although they cut down the risk significantly.
Electrical Fire Protection
While not all electrical arc faults can be prevented, electrical panels can be protected from fire inside the cabinet produced by an arc flash. Automatic fire suppression systems can be installed inside an electrical panel and will provide 24/7 uninterrupted fire protection. The system uses a pressurized Firetrace Detection Tubing that will burst and release clean agent into the cabinet when exposed to the flame. The clean agents are non-conductive, non-corrosive, and leave no residue.
Automatic fire suppression systems provide quick fire suppression right at the source of the fire, limiting equipment damage and preventing the activation of sprinklers. Adding an automatic fire suppression system will contain the fire to the individual cabinet enclosure.