In simple words, an arc flash is an occurrence where a flashover of an electric current, diverts from its intended path and instead travels through the air from one electric conductor to another, or to the ground. During an arch flash, the air acts as a conductor. The resulting effect of an arc flash is usually violent, and when a human being is close when it occurs, serious injuries or even death may occur. An Arc Flash may be caused by several things such as dust, condensation, materials failure, faulty installation, corrosion and even accidental touching.
An arc flash usually expels a huge amount of fatal energy. In the event of arc flash, the arc will cause the surrounding air to be ionized, and the arc flash temperatures will reach more than 35,000 degrees Fahrenheit. This kind of temperatures will not only burn clothing in an instant, but it will also burn a worker’s skin straight away. The resultant temperatures can vaporize of liquefy metals parts such as aluminum, copper or steel equipment which are in proximity. Materials constructed out of metal will expand rapidly as they change from solid state to liquid state.
The pressure waves may knock workers off ladders or off-balance and in some cases throw them across the workplace against other equipment or wall. The sound-blast caused by the Arc-Flash may lead to permanent or temporary hearing loss. All in all, what are some of the factors determine the severity of an Arc Flash?
Factors Determining the Severity of an Arc Flash
- Temperature-An Arc’s temperature is usually determined by the amount of electricity being consumed by the process. The amount of power consumed is usually in megawatts which is a very high volume of energy.
- Time for the circuit to break-Installation of overcurrent protective devices will minimize the duration of the arc flash. The length of the arc is the second most critical factor during an arc flash. Circuit breakers which have been maintained poorly are usually unreliable. If an overcurrent protective device malfunctions, the device will increase the amount of time that it will take to stop or extinguish the fault.
- The cloth’s won-The fabric weight and type of clothing that the worker wears will affect the amount of heat transferred to the worker’s body. The rule is that each of the layer of clothing under the arc related clothing minimizes the amount of heat to worker’s body by around 50 per cent.
- Proximity to the Arc Flash-While working, the employee should stand as far as possible from the equipment. Standing closer to the equipment will increase the incident energy that the employee may receive in case an Arc Flash occurs.
What is An Arc Flash Study?
So as to identify a particular flash hazard on a given equipment within a given facility, the management should conduct an arc flash study. There are numerous software packages which are available which are similar to coordination study and short circuit study software packages. An arc flash study must be conducted by a qualified electrical engineer.
Before an arc flash study is conducted, a coordination study and short circuit study must be performed first, or the results of a coordination and short circuit should be readily available. The result from the final study will classify the hazard at each equipment based on the event energy. Additionally, the Arc Flash study will also establish the Arc-flash Protection Boundary. Within the Arc-flash Protection Boundary, the worker must have the Personal Protective Equipment or proper clothing on.
The main function of the Personal Protective Equipment is to minimize the chances of the employee’s body from a resultant arc flash event to a tolerable level.
Arc flash hazard is an area which is still undergoing increased scrutiny and discussion in the present’s safety conscious environment. The main aim of these standards in this area is to offer an increased safety levels for workers. Individuals involved in the implementation, evaluation and design of electrical systems should have a deeper understanding of an Arc Flash Hazard, minimize the hazard to the worker and also how to evaluate the Arc Flash Hazard.