Arc Flash Analysis: A Project Overview for Electrical Contractors
By Bryan Rupert, Contributor
The process can be daunting for those contractors who are considering undertaking an arc flash analysis for a client. An arc flash analysis is initiated to evaluate the potential incident energy of an arc flash occurrence. The findings from an arc flash study are used to set arc flash protection boundaries and to help prevent injury by designating the appropriate level of personal protective equipment (PPE) required to interface with a particular electrical circuit or conductor.
Here we’ll cover the basics, enough to get you started on assessing your suitability for performing the study. The goal is to provide you with enough basic information to determine where you may need more training and when it makes sense to subcontract parts of the study to more knowledgeable and experienced electrical safety workers, electricians, and/or engineers.
Important Questions for Scoping the Project
As with most any project, an arc flash analysis begins by determining the scope of work. When you work with client companies to define scope, it’s important to ask these three questions:
- Will we be breaking the project down based on equipment voltage levels? Any facility could potentially have three or four voltage levels, or more, so a project could be scoped based on those levels. For example:
- 15kV to 600V
- 600V to 300V
- Under 300V
- Will we proceed through small transformers? Two things to consider when making this decision:
- Keep in mind that “small” is relative, and the client’s decision can have a profound effect on cost.
- In addition, a circuit feed from a single transformer equal to or smaller than 112.5kVA @ 208V is currently exempt from arc flash engineering studies, although this may be changing. Refer to IEEE 1584, published in 2002, for current information.
- Will the project be rolled out in phases? If so, where does each phase start and end.
When you’re ready to estimate the number of points in the study, it’s important to clearly define terminology. For our purposes, a single, electrical data-collection point includes feeder wires, protected devices, and the load—in other words, one complete circuit that requires a label. Although point count figures prominently in the estimating of a project’s cost and time, keep in mind that actual point count will most likely change by the end of the data collection process; therefore, it’s important to keep your estimate flexible to allow for additional points discovered during data collection.
Gather as much point information as possible up front to ensure accurate project estimating. The value of a thorough walkthrough with a knowledgeable person from the client site cannot be overstated. In addition to the walkthrough, the following can also assist in scoping the number of points in an arc flash study:
- Evaluating an existing one-line diagram of the facility
- Reviewing an asset list and/or floor plans that include electrical distribution
- Studying diagrams or lists for a building with a similar footprint
- Researching historical electrical maintenance reports
- Reviewing existing photos of electrical distribution
Data collection refers to the start of the field work portion of the arc flash analysis process. It involves locating and identifying electrical data collection points by a qualified data collection worker. This person should be familiar with the design and construction of the electrical equipment in the facility and knowledgeable about the level of risk associated with the equipment and the appropriate PPE required to mitigate that risk. A rule of thumb in the industry stipulates that a qualified worker should be able to collect at least 35 points a day in an “average facility”—roughly four points an hour. Recognize, though, that it is more complicated to collect data and rate arc flash potential in facilities like hospitals and other vital installations that require maintenance staff to service equipment without powering it down.
Following are suggestions for implementing a successful data collection effort:
- Use available tools for performing data collection. Examples include:
- Templates or spreadsheets that are available online or on paper
- Software tools designed for data collection (like FlashTrack®)
- Log all point data in a neat and uniform manner.
- Collect photos of each point, including existing nameplate information from the device and breaker settings. Although photos are not required, they are considered a best practice in the industry. Photos are especially useful for two reasons:
- Engineers can more readily evaluate the state of the equipment
- Downstream label installation and asset management becomes much easier
- Create a field one-line diagram or use an area of your template or spreadsheet to establish the relationship between sections of equipment.
Engineering Evaluation and Interpretation
Now, it’s time to hand off to a licensed engineer for evaluating and interpreting the collected data. It’s important that contractors engage experienced and knowledgeable engineers trained in assessing power systems. For this reason, many electrical contractors subcontract this work to appropriate sources.
The licensed engineer is responsible for performing the necessary incident energy calculations and establishing whether each circuit meets the national electric code. These incident energy calculations will be used to determine arc flash boundaries and PPE required at each point location. In my experience, approximately 90% of code violations are due to protective devices (i.e., fuses or breakers) being mismatched to the associated wire. Other benefits of the engineering portion of the study include the opportunity to evaluate the equipment’s ability to contain a short circuit and finding hints that the system may have potential coordination issues. These are just a few examples that illustrate why the engineering calculations and findings are crucial to a successful arc flash analysis.
Besides interpreting the data and creating the incident energy calculations, the following also result from engineering collaboration:
- Arc flash one-line diagrams are created, usually with the help of an arc-flash evaluation software program
- Electricians review the arc flash one-line diagrams for accuracy
- Client representatives review the one-line diagrams for correct nomenclature (According to code, every point is required to be named)
Once the client has signed off on the engineering review, an analysis report containing findings and recommendations can be created and you’re ready to print labels for installation. However, an experienced contractor would instead use this time to perform mitigation or coordination, as these activities will most definitely impact the label outcome.
Mitigation or Coordination
Working with the engineering reports, an experienced contractor, typically with the help of engineering, reviews the incident energy levels to determine if they are acceptable and typical for each device in the system. Depending on the facility type and the purpose of the device, you may arrive at a decision to mitigate the findings—in other words, look for ways to reduce incident energy of an arc flash and thereby increase safety. Or you may choose to completely focus on coordination—protecting wires and devices without regard for life safety.
When mitigating, you might find opportunities to de-energize, if it makes sense, or increase working distance and/or ramp up PPE. Any of these changes will impact label content, thus the reason for delaying label printing and installation until after mitigation.
Once labels are printed, it’s important that they be installed in the correct locations; therefore, the task needs to be assigned to someone familiar with the facility and the equipment. It’s here, during label installation, and during asset management, that the contractor and the client realize the full benefit of the time taken earlier to photograph and catalog each of the points. Following are standard guidelines and best practices for label installation: (For complete information, refer to the NFPA 70E 2015 electrical safety standard.)
- Affix each label to the appropriate device
- Place each label so a qualified technician working on the device can easily read the label
- In addition to the required label information such as date, voltage, highest hazard risk category, etc., as a best practice, you should also ensure that each label contains the following:
- A name that matches the nomenclature from the arc flash one-line diagram
- Glove class
- Approach boundary indicators
- The name of the upstream protective device
All the work that went into collecting, cataloging, mitigating, and labeling points is only useful if your client understands the importance of training qualified workers to read the labels and implement the necessary boundary information and PPE guidelines. Therefore, any thorough arc flash analysis process should include a training program for qualified workers. Per the NFPA 70E 2015 standard, this training must be repeated in intervals not to exceed three years. The program should educate attendees on the guidelines for what constitutes a “qualified” worker and to what extent a worker is considered “qualified.”
- The requirements for being considered a qualified worker:
- Worker recognizes the degree and extent of an electrical hazard
- Worker understands the PPE requirements for performing a task safely
- Worker is capable of implementing job planning and preparation steps for minimizing risk
- Who is not a qualified worker:
- Someone who does not have the skills and knowledge to operate the electrical equipment
- Someone who has not had the training to recognize hazards associated with a particular task or equipment
Additionally, the client needs to understand the importance of PPE in the safety equation. To assist in that understanding, experienced contractors should collaborate with their clients to determine what level of PPE should be provided to a client’s qualified workers. PPE decisions should take the following into consideration, within reason:
- The budget limitations of the safety program
- The incident energy levels contained in the resulting arc flash report
- The skill levels of the workers involved
PPE technology changes frequently, so it’s also important for contractors to stay up to date on the latest offerings regarding new products, materials, and fit and to share that information with clients.
When a competent program is handled well—from initial data collection through employee training—the contractor and the client can know they’ve done their best to minimize the risks associated with arc flash. ESW
Bryan Rupert is co-founder and lead consultant at Facility Results, a Plymouth, MI, company that designs and markets an extensive collection of electrical reliability and safety solutions, including FlashTrack™, the company’s award-winning, flagship software package for performing arc flash analyses. (www.FacilityResults.com)