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Solar Arc Flash Safety Series Part One: Warning Labels & Working on Energized Systems

Over the last decade, solar prices have declined 54 percent, allowing the solar market to experience an annual average growth rate of 24 percent. The percentage of electricity that comes from solar in the country is also eleven times higher than it was a decade ago. With the anticipated continued growth of the solar industry in the years to come, it’s more important than ever to exercise safety to prevent any unnecessary accidents. Arc flashes, or the rapid release of thermal energy, pressure waves and electromagnetic interference from a high power electrical system caused by such events as unintentional shorting or equipment malfunction, remain one of top safety concerns for solar professionals. In fact, the Bureau of Labor Statistics found that between five to ten arc fault incidents occur every day in the U.S. According to the Occupational Safety and Health Administration (OSHA), arch flash burns are one of the top three most common hazards when working with energized electrical equipment, with two out of three arch flash incidents resulting from human error. Below we cover the efficacy of arc flash warning labels, and whether working on energized electrical equipment should ever be required.

The Efficacy of Arc Flash Warning Labels

Arc flash labels are a commonplace requirement for solar projects, as they should be. Many times, however, it seems that the arc flash studies and resulting labels are just a ‘check-the-box’ exercise. There never seem to be any follow-up questions regarding the integration of the labels and their values into an effective and safe operations and maintenance plan. Engineers will generate these labels all day, but they don’t have to ever actually use them.

Here is a description of why engineers use arc flash labels:

“Arc flash labels are designed to keep people safe. NFPA-70E was developed at OSHA’s request and sets the standards for electrical safety in the workplace. Arc flash labeling requirements are defined by the newly updated NFPA 70E 2021 standard. The goal of this regulation is to protect personnel by reducing exposure to major electrical hazards. The regulation helps companies and employees avoid workplace injuries and fatalities.”

The “exposure to major electrical hazards” should be avoided, so the required warning labels provide an on-the-spot reminder of the importance of Personal Protective Equipment (PPE) when working on energized electrical equipment and the extreme hazards that can be present. This makes it sound like “hot” work on energized electrical systems is a routine practice, which it should not be. Also, when you look at the Safety Hierarchy of Controls (Figure 1), putting on PPE is the sixth, last, and least effective thing to do when it comes to electrical hazards.

Hot Electrical Work: To Be or Not to Be

This brings us to the question of: is it important to ever do any work live? Here was the scenario given by a British Safety expert to Castillo Engineering’s annual electrical safety training class from Baghdad: There is heavy nighttime fighting going on, shrapnel cuts the power lines to the hospital and the emergency generators don’t start; Do you then rush to splice the wires back together hot because lives are really on the line, time is of the essence, and it is a relatively simple task? His answer was an emphatic “No.” There could be more damage than you initially saw, and re-energizing with your quick splice could cause more equipment damage that substantially prolongs the outage. The unforeseen conditions could also injure you and there may be no immediate qualified backup personnel, which would also prolong the outage. Do the work de-energized, thoroughly check and de-energize the work area, fully inspect and test to determine the scope of work, make the repairs, check again, and then re-energize safely. There are no shortcuts.

If that scenario does not justify working on electrically energized components, can you come up with any important reason for working on an electrically energized solar energy system? Neither can we. Losing solar production is never a reason for performing live work. Solar panels are farming the sun, and just like any dirt-farming activity, a few hours less of sun is not going to affect the big picture. The need for “routine” live troubleshooting will be covered in subsequent blog posts in this safety series.

Castillo Engineering does occasionally receive client comments that they don’t want to see any PPE categories above a Level 3. First, that sort of comment is coming from an unfortunate perspective which is assuming that live work may be needed at any time for any item of equipment. Second, that perspective is also starting out at the wrong end of the pyramid. And third, there are other precautions that could have been taken to have prevented PPE categories from rising about a Level 3. For example, splitting a 4,000 kWac system into two, 2,000 kVA Medium Voltage Transformers powering 2,000 kW inverters each is preferable, instead of going with a single 4,000 kVA transformer feeding a single 4,000 kW central inverter which guarantees extremely high ac and dc arc flash energies on at least one side of the overcurrent protective devices. Some high arc flash hazards are built-in by equipment selection long before the Engineer of Record starts the detailed design and can significantly influence the eventual arc flash levels.

Stay tuned for Part Two of our Solar Arc Flash Safety Series, in which we will cover solar arc flash modeling and routine troubleshooting. Do you have utility-scale solar design and engineering questions? Get in touch with one of our experts today.


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