The effects of this can be seen on adjacent walls and equipment - they are often ablated and eroded from the radiant effects. Surfaces of nearby objects, including people, absorb this energy and are instantly heated to vaporizing temperatures. The metal plasma arc produces tremendous amounts of light energy from far infrared to ultraviolet.

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. For example, when copper vaporizes it suddenly expands by a factor of 67,000 in volume.

During the arc flash, electrical energy vaporizes the metal, which changes from solid state to gas vapor, expanding it with explosive force. The result of the violent event can cause destruction of equipment involved, fire, and injury not only to an electrical worker but also to bystanders. A typical arc flash incident can be inconsequential but could conceivably easily produce a more severe explosion (see calculation below). The massive energy released in the fault rapidly vaporizes the metal conductors involved, blasting molten metal and expanding plasma outward with extraordinary force. When an uncontrolled arc forms at high voltages, and especially where large supply-wires or high-current conductors are used, arc flashes can produce deafening noises, supersonic concussive-forces, super-heated shrapnel, temperatures far greater than the Sun's surface, and intense, high-energy radiation capable of vaporizing nearby materials.Īrc flash temperatures can reach or exceed 35,000 ☏ (19,400 ☌) at the arc terminals. Welding arcs can easily turn steel into a liquid with an average of only 24 DC volts. Electrical arcs, when well controlled and fed by limited energy, produce very bright light, and are used in arc lamps (enclosed, or with open electrodes), for welding, plasma cutting, and other industrial applications. Therefore, as the arc develops and gets hotter the resistance drops, drawing more and more current (runaway) until some part of the system melts, trips, or evaporates, providing enough distance to break the circuit and extinguish the arc. Electrical arcs experience negative incremental resistance, which causes the electrical resistance to decrease as the arc temperature increases. The intense burst of radiation easily penetrates the shade #10 welding filter which shields the camera.Īn 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. With an arc temperature of 17,000 K (30,100 ☏), the radiation output is centered at 170 nanometers, in the far UV.

Even though the energy level used is fairly low (85 joules), the low-impedance, low-inductance circuit produces a flash of 24,000,000 watts. However, the phenomenon of the arc blast is sometimes used to extinguish the electric arc by some types of self-blast–chamber circuit breakers.ĭefinition A controlled arc-flash, produced in a flashtube. (For example, category-4 arc-flash protection, similar to a bomb suit, is unlikely to protect a person from the concussion of a very large blast, although it may prevent the worker from being vaporized by the intense light of the flash.) For this reason, other safety precautions are usually taken in addition to wearing PPE, helping to prevent injury. For example, personal protective equipment (PPE) can be used to effectively shield a worker from the radiation of an arc flash, but that same PPE may likely be ineffective against the flying objects, molten metal, and violent concussion that the arc blast can produce. Both are part of the same arc fault, and are often referred to as simply an arc flash, but from a safety standpoint they are often treated separately. An electric arc between two nailsĪn arc flash is the light and heat produced as part of an arc fault, a type of electrical explosion or discharge that results from a connection through air to ground or another voltage phase in an electrical system.Īrc flash is distinctly different from the arc blast, which is the supersonic shockwave produced when the uncontrolled arc vaporizes the metal conductors. For the related medical problem that can be caused by this, see Arc eye.

What are arc flash boundaries based on