Many electrical contractors woke up this morning to the same inquiry. A former customer needs electrical help, and the only place they know to turn to is the sticker on their electrical equipment that identifies the electrical contractor that installed it. 

However, far too often, the customer knows very little about what the problem is or how they should have cared for the building’s electrical infrastructure. In these scenarios, the electrical contractor is essentially flying blind when they arrive to service the installation. 

The question then becomes, where do we start to complete the job? But more important, where do we start to complete the job safely?

What’s in a risk assessment?

Without a doubt, the starting point needs to be in understanding how to perform the necessary electrical hazard risk assessments so the electrical worker has an accurate picture of what they are up against. Therefore, let’s look at what a risk assessment entails and all the information that must go into one. 

First, there are two electrical hazard risk assessments that NFPA 70E, Standard for Electrical Safety in the Workplace, requires to be performed: an electric shock and an arc flash risk assessment. However, do you fully understand the purpose of these risk assessments? Too often, workers view them as a method for simply determining all the information NFPA 70E states the owner must place on certain electrical equipment labels.

For electric shock and arc flash risk assessments, NFPA 70E states that the risk assessments must be performed to:

Identify if a hazard exists

Estimate the likelihood of the occurrence of injury or damage to health from each hazard

Estimate the potential severity of injury or damage to health

Determine if additional protective measures are required.

While the label affixed to the equipment assists in performing this task, it is only a portion of the process. For installations with no label, the risk assessment must be performed from start to finish on-site. Let’s examine each of these bullets and how they help workers see the entire picture of the work they are about to do.

Electric shock assessment

First, how do we identify if an electric shock hazard is present? There are two predominant ways an individual can be shocked: touch potential and step potential. While step potential is a significant issue, the focus here will be on touch potential. However, if you are working around medium- or high-voltage conductors, step potential should also be included in your electric shock risk assessment. 

So, how do we know when potential hazards are present? This is usually simple to assess. Basically, it boils down to whether there are exposed energized electrical conductors or circuit parts present and how close the worker will need to be to perform the work.

NFPA 70E defines an approach boundary as the distance from exposed energized electrical conductors and circuit parts within which an electric shock hazard exists. This is the limited approach boundary, and the distances can be found in Table 130.4(E)(a) or Table 130.4(E)(b), depending on whether the system is AC or DC. These tables also specify two different types of limited approach boundary: one for exposed movable conductors and another for exposed fixed circuit parts. 

Once we know the work involves exposed energized circuit parts and we will be within the limited approach boundary, we need to get an estimate of how likely we are to be injured. You might have guessed this already, but NFPA 70E has a boundary for this, too. 

The restricted approach boundary is defined as the distance from the same exposed energized electrical conductors or circuit parts within which there is an increased likelihood of electric shock. This could be due to either a worker’s inadvertent movement (accidental contact) or to electrical arc-over, meaning the electricity can jump out and reach the worker. If your work involves entering the restricted approach boundary, you are at an increased likelihood of being shocked and will likely require additional protection. 

The last step in the electric shock risk assessment is to estimate the potential severity and determine what protective measure, if any, we will need to mitigate the risk of injury from contact with energized circuit parts. To do this, we need to determine the severity of the shock if contact is made. Luckily, OSHA has provided guidance on this subject. OSHA sets a voltage “boundary,” so to speak, at 50V—regardless of AC or DC—as being the level at which the electric shock has the potential to be fatal and, therefore, the worker must be protected from any source of voltage above this number. 

However, additional protective measures will be selected based on the nominal system voltage. For instance, measuring voltage on a 480V system often only requires rubber insulating gloves, whereas working around 13.8-kilovolt energized conductors will often require a live-line tool to keep the worker at a greater distance from the energized conductors. So, essentially, the shock risk assessment boils down to identifying whether there are exposed energized circuit parts, how close you will need to approach them and what voltage is present. 

Arc flash assessment

Next, we will need to take a similar approach to performing the arc flash risk assessment. However, this process involves many additional variables.

First, and maybe most important, what are we doing? Energized conductors or circuit parts do not need to be exposed for an arc flash incident to occur. Nor is there an arc flash hazard present every time there are exposed energized circuit parts. So, where do we start on this process? 

Look at the equipment and ask some questions. Does the equipment have a label on it that lists the voltage and arc flash boundary? Is there some nugget of information that will help the worker select PPE? If so, has this label been reviewed for accuracy within the last five years? 

Ask the customer questions about the equipment’s operating condition. This might not matter for certain tasks such as putting probes to energized circuit parts. 

But for some, the operating condition is the difference between a likelihood of occurrence or not, such as operating a switch or circuit breaker. 

Does the customer know if the equipment has been properly maintained? Is the equipment being used in accordance with the manufacturer’s instructions? Is the interrupting rating and short-circuit current rating accurate for the available fault current? Are all the doors and covers closed and secured properly? Is there evidence of impending failure of the equipment?

Once these questions have been answered, consult Table 130.5(C) for guidance on whether the task presents a likelihood of an arc flash occurring. If the answer is yes, we now need to know if we must be within the arc flash boundary (AFB) to perform the task. Of course, this is much easier to know if it is on a label. If not, we can consult the PPE category method tables to determine the arc flash boundary. More on these tables in just a bit. 

So, if we have identified that the task is likely to cause an arc flash and we will be in the AFB, we need to estimate the potential severity of injury to determine the proper method to mitigate this risk. Just like with the boundary, we will either get a number from the label on the equipment or need to use the PPE category method. However, this method does not indicate the exact energy that will be released during an arc flash. It simply provides guidance on what type of PPE is required based on the equipment type, available fault current, clearing time of the upstream overcurrent protective device and the working distance. 

If your equipment does not meet the criteria of the tables, the only option is to perform an incident energy analysis (arc flash study). Once you have either an incident energy number or a PPE category, you can select what, if any, protective measures are to be taken.

Protective measures

Finally, when it comes to selecting additional protective measures, NFPA 70E requires employers to develop an overall electrical safety program that minimizes the risk of injury from electrical hazards in accordance with an established Hierarchy of Risk Control Methods. Not every method for controlling risk of injury is created equal, and some are better than others. 

At one end of the spectrum, there is hazard elimination, substitution and engineering controls, which seek to reduce the likelihood of the event from occurring. 

On the other end, we find items such as administrative controls (procedures), awareness controls (labels) and PPE. This less-effective grouping can minimize certain aspects of likelihood of occurrence, but it’s not likely to prevent them completely. For example, following a standard operating procedure doesn’t mean you will never accidentally touch energized conductors. The only thing PPE takes aim at is the potential severity of injury after the incident has occurred. This makes PPE the least effective tool in the toolbox for minimizing the risk of injury. However, that does not mean PPE is not effective. It means there are methods, such as removing the electrical hazards by creating an electrically safe work condition, that do a better job than putting on an arc flash suit to reduce risk of injury.

Understanding how to assess the risk of injury from electrical hazards is at the center of what it means to be a qualified electrical worker. If we learn to do this effectively, it means there won’t be many situations we can’t handle. If nothing else, knowing how to perform proper risk assessments helps us avoid getting in over our heads. 

Next time you get the call to go back to service an installation that has been energized and running for a while, remember the first step starts with assessing the risk associated with the work and then selecting the proper means to mitigate this risk before you begin work. 

Until next time, stay safe and remember to always test before you touch!  

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