Arc flash study

The assessment of arc flash hazards within a system and its working environment is termed an arc flash study, alternatively known as an arc flash hazard analysis. This electrical engineering examination scrutinizes the electrical distribution system of a facility to assess the incident energy associated with a potential arc flash event, delineates safety boundaries, and stipulates Personal Protective Equipment (PPE) requirements. Additionally, the results of arc flash study help to generate warning labels to be affixed to individual electrical equipment, documenting incident energy levels and also help to provide recommendations on how to make the power supply system more reliable and safer.

Per regulations outlined by OSHA and NFPA 70E, arc flash studies must be conducted every five years or following any significant changes or updates to the electrical system.

The arc flash study provides estimated calculations of short-circuit currents, tripping times, and incident energy (arc flash energy). Additionally, it assesses coordination to mitigate arc flash energy levels while aiming to eliminate nuisance tripping, whether during a ground fault or phase fault condition.

The objectives of the arc flash risk assessment are:

Identification of arc flash hazards.

Determination of the necessity for additional protective measures.

Estimation of the likelihood of occurrence and potential severity of injury or health damage.

The arc flash study calculates short-circuit currents and tripping times, essential for electrical safety. Furthermore, the arc flash assessment reviews coordination to decrease incident energy levels while focusing on eliminating disruptions, be it during ground faults or inter-phase fault conditions.

Presently, the majority of arc flash hazard risk studies and assessments adhere to IEEE 1584 and NFPA 70E standards. According to NFPA 70E, arc flash studies must be conducted every five years or whenever significant modifications are made to the facility.

The primary rationale for conducting arc flash studies or assessments is to prioritize personnel safety. Short circuit and arc flash faults pose significant risks to individuals, with potential fatal consequences. Arc flash exposure often leads to severe burns, visual impairment, ruptured eardrums, lung damage, psychological trauma, and even fatalities.

Arc flash hazard analysis is indispensable for assessing the risk posed to personnel and informing workers about the appropriate personal protective equipment necessary when working on energized electrical equipment.

Another crucial reason for conducting arc flash studies or assessments is to fulfill obligations and comply with government regulations.

Practical Steps for Conducting an Arc Flash Hazard Study

Step 1

Identification of Sites and Equipment during which we identify locations with arc flash risk, at the same time exclude equipment where arc flash risk is negligible.

Step 2

Data Collection Qualified personnel will gather essential data from all relevant electrical equipment, including:

Utility data, such as fault current, operating voltage, and details of protective equipment.

Information on protective devices, including manufacturer, model, settings, and interrupting ratings.

Conductor specifications, covering lengths, sizes, and types of overhead lines, bus ducts, and cables.

Transformer details, including impedance, tap settings, and ratings.

Step 3

Power System Modeling Develop or update one-line diagrams to reflect the current power system configuration and operation modes. Accurate diagrams are crucial for identifying power sources, voltage levels, electrical equipment, and protective devices. We utilize SKM Power Tools for Windows for system modeling and analysis.

Step 4

Short Circuit Study Conduct a short circuit study to determine current magnitude throughout the power system post-fault. This study calculates bolted fault current, essential for incident energy and equipment interrupting ratings. Underrated equipment is identified by comparing ratings with calculated short circuit conditions. We adhere to ANSI Std. C37 and IEEE Std. 141-1993 (Red Book) standards.

Step 5

Protective Device Coordination Perform protective device coordination to ensure protective devices confine over-current effects to a minimal area. Results inform recommendations for arc flash hazard mitigation. While optional, completing this step is essential for arc flash mitigation. We follow IEEE Std. 242-2001 (Buff Book) guidelines.

Step 6

Arc Flash Calculations Based on available short circuit current, protective device clearing time, and arc distance, calculate incident energy levels and flash protection boundaries for relevant equipment buses. Determine arc hazard magnitude using NFPA 70E, IEEE 1584, or NESC Tables 410-1 and 410-2 methods, as applicable.

Step 7

Reporting Prepare your Arc Flash Hazard Analysis Report, allowing for a review period to consider mitigation recommendations. Optionally, hold a Management Summary meeting to interpret report results. Upon approval, provide a final report and full-sized one-line diagrams, certified by our Registered P.E., in digital and hard copy formats.

Step 8

Label Installation Generate and install arc flash hazard warning labels, including incident energy, working distance, nominal voltage, and arc flash boundary. Labels also feature Limited, Restricted, and Prohibited approach boundaries, date, upstream protective device, and recommended personal protective equipment, meeting NFPA 70E 130.3 compliance. Optionally, provide bolted fault current data.

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