![]() ![]() are all signs of deteriorating equipment that cause additional hazards.ĭo most companies have qualified personnel to assess the likelihood that an adverse event may occur, and the severity of the injury if it does?Īrc flashes often occur from minor oversights, so an ideal arc flash hazard assessment should consider a number of risk factors that might not be immediately obvious. Rusted doors, hinges, missing knock-outs, screws, etc. Dust can be a big hazard and even cause arc flash when equipment is operated where "fugitive" dust is present. This is just not true and often leads to a misguided approach to an arc flash. It's the assumption that a downstream little 30A disconnect can't have a hazard greater than its upstream feed. ![]() We see many times that facilities will assess the main gear and even down to the MCC level and then stop. What hazards are most typically often overlooked?īranch circuits, downstream items like disconnects, RTUs on roof tops, even control cabinets. And again, a company needs someone qualified to do the work, which requires technical knowledge that is often lacking This gets back to relying on local resources that are not electrical experts, and the lack of education and awareness on the capability of equipment to product an arc. Why do companies fail to effectively identify and inventory AF risk factors? It can often be that this frequent interaction/exposure increases the likelihood that an arc flash may occur. Typically minor oversights can be common equipment, or equipment that is serviced or interacted with frequently. Why do arc flashes often occur from minor oversights? With arc flash its more difficult to determine what equipment has higher arc flash hazards. With shock hazards it is easy, if you can reach in and touch the "shiny parts" you can get shocked. Although it's not that workplaces assume there isn't a risk, it's just to what level could it be. ARCAD Arc Flash Analytic software automatically selects either IEEE empirical model or Lee method for arc flash calculations based on input system parameters.Very common. For cases where voltage is over 15 kV, or gap is outside the range of the model, the theoretically derived Lee method can be applied. The IEEE procedure is valid for voltages ranging from 208V volts to 15kV with gap ranges between 3 mm. The equations are used to calculate the incident energy and arc flash boundary. IEEE Standard 1584 details the procedure and needed equations for arc flash calculations. The boundary is defined by NFPA 70E as the distance at which the worker is exposed to 1.2 cal/cm 2. In addition, a qualified person must accompany unqualified persons. Persons crossing into the arc flash boundary are required to wear the appropriate Personal Protective Equipment (PPE) as determined by calculating methods contained in NFPA 70E. In some instances, calculations may decrease the boundary distance. NFPA 70E also allows the AFB to be calculated. NFPA 70E establishes the default arc flash boundary at 4 feet for low voltage (< 600V) systems where the total fault exposure is less than 5000 amperes-seconds (fault current in amperes multiplied by the upstream device clearing time in seconds). The AFB is a safe approach distance from energized equipment or parts. The arc flash boundary is based on voltage, the available fault current and the time it takes for the upstream protective device to operate and clear the fault. The arc flash hazard analysis should determine the arc flash boundary (AFB) and level of personal protective equipment (PPE) that the worker must wear. It is important to note that conductors and equipment are considered live when checking for voltage while putting equipment in a safe work condition. Until equipment is placed in a safe work condition (NFPA 70E 2000 Part II 2-1.1.3), it is considered live. Also, NFPA 70E 2000 requires that before a worker approaches exposed electric conductors or circuit parts that have not been placed in a safe work condition, a flash hazard assessment must be performed. The limited, restricted and prohibited approach boundaries are based on the voltage of the energized equipment. There are three shock approach boundaries (limited, restricted and prohibited) required to be observed in NFPA 70E 2000. NFPA 70E has developed requirements to reduce the risk of injury to workers due to shock and arc flash hazards.
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