By Dave Hernandez, Contributor
The methods and requirements for arc flash studies are updated frequently, so it can be tough to know and understand what a complete and valid study looks like. On top of that, companies performing arc flash studies don’t all put the same resources and personnel into their analysis, so quotes can vary wildly when considering multiple proposals. This can lead to a lot of confusion because many of the quotes don’t compare “apples to apples.” Some proposals that offer the lowest cost might be lacking key inspections and data collection or might only go as far as the panel level of the power system.
Here are five ways to recognize you’re getting a complete and accurate arc flash study:
- First, looking at electrical schematics is one of the quickest ways to gauge if an arc flash study is thorough. In a true study, a data collection engineer will be on site to gather information from discreet electrical components and analyze electrical infrastructure. The process includes removing panel covers, inspecting cables, and tracing distances. There are a couple of areas to review in the schematics to judge the quality of the study.
Protective device settings should be accurately shown in the schematic and backed up by supporting data collected by the engineer during the study. Using software helps with calculations, but extra steps are needed to make sure protective device settings are part of the equation and provide the basis for incident energy value of downstream equipment.
Examining cable distances is another easy way to test the quality of a study. The best arc flash studies accurately document distances by walking out unique measurements for each specific cable. Insufficient studies estimate distances. If the distances on the study are rounded to the nearest tenth or hundredth, they’ve probably been estimated. For cables to be traced properly, an engineer should measure them with rolling wheels or laser range finders.
Electrical schematics are one of the driving factors in any complete arc flash study and are one of the most important safety tools, so it’s important to have proper and accurate schematics.
- The second key to a complete arc flash study is the labels. By recognizing the information on the labels, you can determine if a study was performed to the latest and safest standards or if it was done to older standards with fewer safety checks.
Labels are created using a table method or by specific incident energy calculations, but they can’t include both. Labels that provide a PPE category ranging from 0-4 were created prior to 2015 or derived using a generic table method from the NFPA 70E. A true arc flash study uses the incident energy method. Incident energy shows a value on the label in calories per centimeter squared and are based on the IEEE 1584 standard released in 2018. These latest standards include over 1800 tests in 5 configurations, compared to only 300 tests and 2 configurations in the standards released in 2002. Any company performing a proper study should be using incident energy methods and the IEEE guidelines from 2018. More information about incident energy values can be found in the 2021 edition of the NFPA 70E.
- The third key to a complete arc flash study is to make sure it goes past the panel level. All studies must stop somewhere but many low-cost studies arbitrarily stop at the panel level, which can compromise safety because incident energy is not necessarily lower on the load side of the panels.
Robust schematics should show feeder devices off of electrical panels. Check for things like 480V local switches, 50 HP motors, or 240V transformer circuits going to air handler units. Make sure machines and control panels specific to your facility are included.
The IEEE 1584 provides guidance on where studies can stop, but it’s critical to know that an arc flash study should be done anywhere there are employees working near energized equipment or there’s potential to be working on energized equipment rated at 240V or greater or fed from a 125 KVA transformer. Again, accurate schematics will show if these devices are coming off the panels.
- Mitigation recommendations are the fourth way to know an arc flash study is superior. Mitigation recommendations aren’t always required but are a key strategy to improve safety at any facility. An engineer will analyze a completed arc flash study to identify hazards and recommend protective device modifications and upgrades to eliminate, substitute, or reduce hazards.
The Hierarchy of Risk Control Method
The Hierarchy of Risk Control Method starts with the idea that hazards are reduced or removed whenever possible. It’s a six-level process including:
1) Elimination – completely removing the hazard
2) Substitution – minimizing the hazard
3) Engineering controls that isolate employees from the hazard
4) Awareness that alerts employees to the hazard
5) Administrative controls that train employees in the best electrical safety practices
6) PPE worn in accordance with labels
Mitigation recommendations can sometimes be compromised by a case of the “fox guarding the chicken coop.” Major equipment manufacturers performing an arc flash study might recommend upgrades with all new equipment and devices. It’s important to realize many mitigation strategies can be cost effective or implemented for free. It might be as easy as changing instantaneous levels on a breaker. In a lot of cases, instantaneous levels have been left on the highest setting following troubleshooting procedures, but by doing a load study on the circuits and making sure instantaneous levels won’t cause nuisance tripping, the level can be lowered to reduce incident energy values.
- The fifth and final way to know if an arc flash study is complete is a stamp of approval from a professional engineer. All 50 states require that a licensed professional engineer certifies the study in the state where the study is being performed. Some states also mandate firm licensure for the study.
Remember, not all arc flash studies are created the same. To ensure your facility is safe and compliant, it’s important to understand that lower cost studies are usually less accurate and might not provide the best safety solutions. Electrical schematics, labels, the equipment being inspected, mitigation recommendations, and proper licensing are the key components that will help you recognize how complete an arc flash study is. ESW
Dave Hernandez, PE, CEM, GBE, CESCP is a distinguished Professional Engineer licensed in 52 U.S. jurisdictions and serves as the Chief Operating Officer at Electrical Power & Safety Co. (https://epsco.co), a world leader in electrical safety. He has overseen over 20,000 electrical projects, sits on various industry committees, and has published several white papers.