An arc flash is a release of electricity that occurs as the result of an arcing fault between one phase bus bar and another. Due to circuitry design, flashes begin when a problem with circuitry, such as a loss of insulation, facilitates an electrical release. Once in place, however, an arc is sustained by conductive plasma that uses the air as a conductor, until a form of impedance extinguishes it. Depending on voltage and arc impedance, flashes can range from minor to devastating, with the largest ones creating explosions that hurl shrapnel. Because a certain amount of voltage is necessary to facilitate hazardous arcs, dangerous arcing typically occurs in electrical systems where the bus voltage exceeds 120 volts.
What Prevents Flashes from Occurring?
Dangerous arcing has been a concern for as long as electrical systems of 120 volts and above have been in use, with circuit breakers and fuse boxes being the primary mechanisms for their deterrence. Circuit breakers and fuse boxes exist to prevent two occurrences: an overload, in which a circuit receives voltage that is too high to conduct along the established path; and a short circuit, in which low or non-existent impedance creates the perfect situation for dangerous arcing. Under normal conditions, a circuit exposed to too much voltage would "trip" in the case of a breaker panel, or "blow" in the case of a fuse box, breaking the current that would facilitate a dangerous arc.
To ensure that breakers perform as expected, they receive routine maintenance from trained technicians, who perform flash analysis. A fully developed analysis will consist of the following preparatory measures: (1) A one line drawing that identifies all electrical components by name; (2) data regarding the lengths and cross sections of cables; (3) data regarding the minimum and maximum fault currents present at a building's electrical entry point; and (4) other facility information as necessary. With these elements in place, a technician can use their data in equations provided by the NFPA or the IEEE to determine flashing hazard, then adjust a breaker / fuse system to lower flashing hazard as necessary.
What Role Do Generator Services Play?
Facilities have two choices for conducting flash hazard analysis: maintaining a team of in house technicians, or outsourcing their needs to an industrial power services provider, such as generator service provider. With cost savings in mind, many companies opt for the latter, although companies that have technicians in house can also benefit from power provider services in the form of arc flash analysis and training, a discipline that focuses on electrically safe work practices, such as properly assessing flashing hazard in terms of: data gathering, equations used, equipment used, and the latest compliance standards. To learn more about arc flash analysis and training, contact an industrial power services provider today.