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Arc Flash Hazard Analysis

Why Is An Arc Flash Analysis So Essential?

With protection from the dangers of arc flash and arc blast being one of the main focuses of the NFPA 70E, there are few things as important as having a proper and thorough Arc Flash Engineering Study of your facility completed. Not only is it required under OSHA and NFPA 70E regulations, it is what informs your employees and contractors of the danger level associated with testing and working on electrical panels and devices. It also gives individuals who may be performing this testing or work the required information to determine what personal protective equipment (PPE) needs to be worn – the necessary equipment to help protect them from the hazardous situations and often life-threatening burns and injuries that occur as the result of an arc flash incident.

Second degree burns occur at the relatively low incident energy level of just 1.2 calories per centimeter squared, and arc flash incidents are known to kill workers and other unprotected individuals in the area of an incident up to – and beyond – 10 feet away from the source. The Informative Annex K to the NFPA 70E points out that temperatures in a typical arc flash incident can reach 35,000° F and thousands of people are hospitalized or admitted to burn centers each year due to severe burns from arc flash incidents. This is exactly why Wisconsin-based Archer Electric, LLC, urges the use of safe working practices so strongly, always placing equipment in an electrically-safe and de-energized condition before beginning any service or repair, and ALWAYS wearing the appropriate level of PPE for a given task or piece of equipment. The relative danger level of an electrical panel or piece of electrical equipment, expressed as a hazard category, is not something that can be guessed at. This determination of incident energy and related hazard category requires the use of very specific, sophisticated engineering calculations based on numerous component variables that all have to be taken into consideration to accurately generate the available incident energy that any piece of electrical equipment or electrical panel has. This is the main purpose of performing an arc flash hazard analysis engineering study.

Short-Circuit Analysis

A short-circuit analysis provides device trip characteristics and input information for an arc flash hazard analysis engineering study. As part of your equipment evaluation, the short-circuit analysis compares the maximum available fault current against the interrupting rating of system overcurrent protective devices (e.g. breakers, fuses, etc.). In addition to the data that this analysis provides to the overall arc flash hazard analysis, it also makes sure that the overcurrent protective devices in a given system are able to withstand and interrupt the maximum available fault current for the nominal system voltage at their respective line side terminals, as is required by the NEC Standard, Section 110.10. An added function of this short-circuit analysis is the assistance it provides in determining the appropriate devices as well as device settings (most importantly adjustable settings on breakers that will be discussed further in the Coordination Study section below). Further, Archer Electric will provide recommendations for corrective action for those devices that do not pass this short-circuit analysis portion of the equipment evaluation (i.e. where the calculated fault current exceeds the rating of the equipment or protective device).

Coordination Study/Time Current Curve (TCC) Reports

As part of the overall equipment evaluation, an overcurrent device coordination (Time-Current coordination) is performed to determine the appropriateness of existing overcurrent protective devices and settings. The overcurrent protective device equipment evaluation looks at the downstream loads associated with each of the analyzed breakers to determine its ability to appropriately interrupt the load at each bus location. This overall device coordination requires looking at both the maximum protection and maximum continuity factors, balancing these two competing interests to achieve desired facility goals. Further, each of the adjustable overcurrent protective devices is examined in this selective coordination to determine the appropriate settings to help achieve both the system continuity and protection goals, while also avoiding nuisance tripping. The procedure for recommended settings is based on NEC requirements for both normal and emergency systems. Each adjustable overcurrent protective device will receive a time current curve analysis to determine appropriate settings and will be included in the final full-color report.

Coordination Study/Time Current Curve (TCC) Reports

OSHA and NFPA 70E regulations require the labeling of electrical equipment and distribution panels to warn and alert employees of the hazards associated with electrical equipment. Archer Electric provides arc flash warning labels that meet all of the latest requirements of the NFPA 70E standard, and list: the device name; associated protective device; incident energy; nominal voltage; and related category level of PPE to be worn when performing testing or work on a given device. Archer Electric utilizes Brady® thermal transfer labels for this purpose.
As part of the labeling process, we also label applicable panels with name, source, and voltage labels. Additional labels for breaker number and equipment fed by the applicable breakers are also installed on the interior of panels for greater information and ease of identification.