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Arc Flash Study

An arc flash (or arc blast) is a type of electrical explosion that results from a low impedance connection to ground or another voltage source.  An arc flash study is listed as a requirement in the 2012 edition of NFPA 70E Article 130.5, with the labeling requirements listed in Article (130.5(C)).  Having an arc flash study conducted is the responsibility of the facility owner and management which safeguards all employees who come into contact with potentially dangerous work conditions.

Understanding the potential for an arc flash allows the facility equipment to be labeled with appropriate identifiers, including the potential incident energy available at each device or piece of equipment, the appropriate personal protective equipment (PPE) required to protect the individuals that will be in contact or working with the equipment in question. These labels also assist in employee arc flash education. 

It is important to note that an Arc Flash Study is required when a new system is built and also that the study be updated when a major change has been made to an existing system, but not to exceed a five-year time period between updates.

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Device Coordination (AKA Selectivity Study)

Coordination of protective devices is an important part of the design process of a new electrical system.  All protective devices, relays, circuit breakers, and fuses have a trip curve that is specific to that type or model device.  These curves can be set or designed so that in the event of a fault situation the downstream device will trip or operate before the upstream devices.  This will enable the facility to de-energize only the affected branch with the fault and not the entire facility.  An important aspect of device coordination concerns employee safety and making sure that the device settings are quick enough to minimize fault time and will allow the potential fault to clear as quickly as possible.  This also will assist in minimizing property damage.  Coordination of protective devices is also a requirement of NFPA 70B Article 9.3 as well as an ANSI/IEEE requirement. It is important to note that the coordination curves used in software models are based upon properly maintained and lubricated equipment.

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Load Studies

Load-flow studies are a requirement of NFPA 70B article 9.4 and ANSI/IEE 242.  A load-flow study shows the direction and amount of power flowing from available sources to every load within the facility.  This study gives the individuals working with or around the facility equipment an accurate understanding of the amount of current present and the locations that are the most and least heavily loaded within the facility.  

A new load-flow study should be conducted whenever any change occurs in the load flow. This includes changing motors, motor horsepower, transformer size or impedance, any change in operating configurations that were not previously planned, and after adding or removing any correcting capacitor or loads to a facility.

Short Circuit Analysis

A short circuit analysis is a requirement in NFPA 70, NEC Sections 110.9 and 110.10 and is associated closely to load studies, device coordination, and arc flash hazard studies.  A potential short circuit represents a significant amount of destructive energy.  This energy can be mitigated by conducting a coordination study and by increasing the protection available to persons by completing the arc flash hazard analysis. A short circuit analysis should be approached in a manner similar to arc flash and load studies.  Any time that change is performed on the existing systems the short circuit analysis needs to be updated to reflect the changes. This also means that the current short circuit analysis needs to be available for the facilities engineer or supervisor so that they will be aware of the results of the analysis and able to make informed decisions concerning the facility systems.

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304 Turney Ridge Rd
Somerville, AL 35670

41 Peabody Street
Nashville, TN 37210