Arc Flash Study

#safety #industrialsafety #electricalsafety #faultcurrent

What is Arc Flash Analysis???

An arc flash analysis is essentially a risk assessment of a particular environment within a workplace that determines what arc flash hazards are present.

Who can perform an Arc Flash Analysis?

An arc flash analysis should only be performed by experienced and qualified electrical engineers familiar with power quality, short circuit studies, NFPA 70E, and IEEE 1584.

In order to properly identify and calculate Arc Flash Incident?Energy certain steps need to be done.

Step 1: Data Collection Process

Collect data by visiting the site, gathering documentation and creating operation scenarios.

Step 2: Develop Single Line Diagram

An electrical single-line diagram is a blueprint of the electrical system. Creating a one-line diagram is the first step in preparing a critical response plan, enabling electrical personnel to fully understand the layout and design of the electrical system.

Step 3: System Modelling

·??????? Determine enclosure type, dimensions and typical gap

·??????? Determine electrode configuration

·??????? Determine working distance

·??????? Model protective device characteristics

Step 4: Arcing Short Circuit Calculations

Calculate the bolted fault currents from the data gathered in Step 1 and Step 2. Refer to IEEE Std for details on methodology pertaining to these calculations. The typical method is to enter the data into a commercially available software program that allows you to model your system and easily switch between modes of operation. The bolted fault current calculated for each point in the system represents the highest possible fault current expected to flow to that point.

Step 5 : Time-Current Curve Evaluation

IEEE 1584 offers guidance on using the time-current curves of overcurrent protective devices including how to handle average-melt-time-only curves and relay-operated circuit breakers, for example. For certain types of current limiting fuses, time-current curves are not required, because their characteristics have been incorporated into the final Flash Protection Boundary and incident energy equations.

Step 6: Incident Energy Calculations

These calculations provide heat energy densities in either cal/cm2 or joules/cm2, values necessary in selecting appropriate PPE and FR clothing. Because of the complexity and number of manual calculations

possible, software is recommended to complete this step. Most software gives you a choice of equations, including three other incident energy equations identified in Appendix D of NFPA 70E. Factors affecting the choice of equations include: type of equipment, voltage levels, and protective devices. A spreadsheet-type calculator is included with IEEE 1584 and can be useful for sample calculations and small systems.

Step 7: Arc Flash Boundary

The Arc-Flash Boundary is the distance from the arc source at which the onset of a second-degree burn could occur. The default and recommended value is 1.2 cal/cm2.? However, if your safety program requires everyone at all times to wear PPE, then based on engineering supervision, the value of EB can be set to a value higher than 1.2 cal/cm2.

Step 8: Determine Personal Protective Equipment Requirements

The most recent NFPA 70E standard identifies 4 PPE categories related to incident energy analyses. Each number represents an increased risk of danger and requires a higher level of PPE as shown below.

Step 9: Arc Flash Warning Labels

It is recommended to paste the Arc Flash labels on the front side of every panel to create awareness among the workers.

The labels have the details of Incident energy level, Working distance, Limited approach boundary, Restricted approach boundary, Arc Flash boundary, and recommended Arc Rated PPE.

Step 10: Develop the Report and Recommendations

All activities related should provide recommendations, supporting electrical engineering design activities based on the model.

Step 11: Integrate the Study into the Electrical Safety Program

Employers are required to conduct these assessments in order to ensure that their workers understand the risks posed to them and how best to protect against them.

Step 12: Training

On-site training at the customer's location to identify needs for knowledge and discussion about safety.

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