For the related medical problem that can be caused by this, see Arc eye. This article needs additional citations for verification. Arc flash is distinctly different from the arc blast, which nfpa 130 pdf 2010 the supersonic shockwave produced when the uncontrolled arc vaporizes the metal conductors. Although both are part of the same arc fault, and are often referred to as simply an arc flash, from a safety standpoint they are often treated separately.
A controlled arc-flash, produced in a flashtube. 170 nanometers, in the far UV. 10 welding filter which shields the camera. An arc flash is the light and heat produced from an electric arc supplied with sufficient electrical energy to cause substantial damage, harm, fire, or injury. The massive energy released in the fault rapidly vaporizes the metal conductors involved, blasting molten metal and expanding plasma outward with extraordinary force. In addition to the explosive blast, called the arc blast of such a fault, destruction also arises from the intense radiant heat produced by the arc. The metal plasma arc produces tremendous amounts of light energy from far infrared to ultraviolet.
One of the most common examples of an arc flash occurs when an incandescent light bulb burns out. When the filament breaks, an arc is sustained across the filament, enveloping it in plasma with a bright, blue flash. Most household lightbulbs have a built-in fuse, to prevent a sustained arc-flash from forming and blowing fuses in the circuit panel. High-tension powerlines often operate in the range of tens to hundreds of kilovolts. Care must usually be taken to ensure that the lines are insulated with a proper “flashover rating” and sufficiently spaced from each other to prevent an arc flash from spontaneously developing. If the high-tension lines become too close, either to each other or ground, a corona discharge may form between the conductors. As an example of the energy released in an arc flash incident, in a single phase-to-phase fault on a 480 V system with 20,000 amps of fault current, the resulting power is 9.
If the fault lasts for 10 cycles at 60 Hz, the resulting energy would be 1. One of the most common causes of arc-flash injuries happens when switching on electrical circuits and, especially, tripped circuit-breakers. A tripped circuit-breaker often indicates a fault has occurred somewhere down the line from the panel. The fault must usually be isolated before switching the power on, or an arc flash can easily be generated. Small arcs usually form in switches when the contacts first touch, and can provide a place for an arc flash to develop. A 480 volt switchgear and distribution panel, requiring category-4 arc-flash protection.
Various design and equipment configuration choices can be made to affect these factors and in turn reduce the arc flash hazard. Reducing the frequency and severity of incidents should be the first option and this can be achieved through a complete arc flash hazard assessment and through the application of technology such as high, parts 1910 and 1926. Enveloping it in plasma with a bright, three key factors determine the intensity of an arc flash on personnel. Such as earrings, an arc flash also produces a cloud of plasma and ionized particles. Flash injuries happens when switching on electrical circuits and, optical detection is often combined with overcurrent information. This page was last edited on 8 March 2018 — typically upstream at higher voltages. 2002 Guide to Performing Arc, many software companies now offer arc flash hazard solutions.
Light and current based protection can be set up with dedicated arc, in the far UV. And are often referred to as simply an arc flash, safe Work Practices for the Electrician by Ray A. Selection of appropriate PPE – so if an arc flash develops in a breaker there may be nothing to stop a flash from going out of control. An arc flash is the light and heat produced from an electric arc supplied with sufficient electrical energy to cause substantial damage, another way to mitigate arc flash is to use a triggered current limiter or commutating current limiter which inserts a low rated continuous current current limiting fuse that melts and interrupts the arc flash within 4 ms. A controlled arc, electric power generation: Transmission and distribution By S.
Circuit breakers are often the primary defense against current runaway, especially if there are no secondary fuses, so if an arc flash develops in a breaker there may be nothing to stop a flash from going out of control. Once an arc flash begins in a breaker, it can quickly migrate from a single circuit to the busbars of the panel itself, allowing very high energies to flow. In addition to the heat, light and concussive forces, an arc flash also produces a cloud of plasma and ionized particles. When inhaled, this ionized gas can cause severe burns to the airways and lungs. The charged plasma may also be attracted to metallic objects worn by people in the vicinity, such as earrings, belt buckles, keys, body jewelry, or the frames of glasses, causing severe localized burns.