An arc flash event can expel large amounts of deadly energy in the form of excess heat, vaporized metal, explosive pressure, and intense sound waves. An arc flash occurs when an inadvertent low-impedance connection established through the air between energized phase conductors or with a ground conductor. Proper electrical system design and construction, using an active solution, can mitigate or virtually eliminate the hazards associated with arc flash.
A Passive Solution – Arc Resistant Switchgear
A commonly-used passive approach involves using arc resistant switchgear. An arc resistant switchgear is a specially designed equipment that utilizes heavy rugged construction to internally contain an arc flash within the structure and redirect it elsewhere. A passive solution is inadequate because it will not reduce the intensity or duration of an arc flash event. As a result, the internal equipment damage will still be significant, requiring costly repairs, or possible replacement. Furthermore, arc-resistant switchgear can cost 20% more than the standard switchgear and yet they are not available in electrical ratings required to supply heavy industrial applications.
An Active Solution – Arc Energy Reduction Switches
This philosophy consists of utilizing an arc energy reduction switch to reduce the intensity of arc flash incident energy. Whenever operation or maintenance is performed on electrical equipment, a qualified electrician would toggle a selector switch on the upstream breaker to establish high-speed tripping. When designed properly, this fast-tripping of the breaker will significantly mitigate an arc flash event.
An Active Solution – Differential Relaying
This philosophy consists of establishing a zone of bus differential protection within a switchgear lineup. When the current-sensing elements within the bus differential protection zone senses an anomaly such as an arc flash event, high-speed tripping is initiated. When designed properly, this fast-tripping will significantly mitigate an arc flash event.
An Active Solution – Optical Sensing
This philosophy consists of utilizing optical sensors that are strategically placed within a switchgear lineup. The optical sensors monitor the emittance of intense light that is discharged during an arc flash event. Whenever the optical sensors detect the light release from an arc flash event, high-speed tripping is initiated. When designed properly, this fast-tripping will also quickly extinguish an arc flash event.
An Active Solution – Remote Operation
This philosophy consists of performing all energized operation and maintenance at a remote location away from the switchgear. This consists of designing specialized equipment that allows remote open/close operations and remote racking of breakers. When properly used, this approach virtually eliminates all electrical operation and maintenance hazards associated with arc flash.
An active solution for mitigating and eliminating arc flash hazards is always better than a passive solution. With proper and careful design, electrical systems can be built for optimizing personnel safety. For more information on how to optimize arc flash safety for your electrical system, feel free to call me at (240) 582-3900 — Priyan De Silva, Helios Electric LLC.