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Leadership Discussion

Education and Loss Prevention Department Leadership Blog. Tips for leaders, ideas for prefab, safety tips, code ideas, announcements and more. 

 

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The importance of testing for an absence of voltage.

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Human error can't be eliminated. Nobody's perfect. No matter what we do, mistakes will happen. The Standard for Electrical Safety in the Workplace starts with this principle. It's the foundation of our electrical safety policy (NFPA 70e). Five people die every day due to human error in the construction industry in the United States, and many of them are electrical accidents. 


An employee was shocked while working on equipment that had been locked out on a recent project. For the first time, the project was energized the week before, successfully. Despite numerous challenges and obstacles placed in the team's path, the project was completed with a lot of hard work and accomplishment. Coordination, planning, energized work permits, and lock out tag out went well. 


Some pieces of equipment needed to be completed and crews were assigned to do that. Meanwhile, commissioning was energizing and testing equipment. They were coordinating to make sure the commissioning crews weren't working on the same arrays as the completion crews.  One of the guys doing the completion work got shocked terminating a DC feeder into a load break. The shock was low enough that the person only got a small burn.  


After investigating the situation, it was determined that the equipment that person was working on was in an array that was locked out, and all the DC harnesses had been disconnected. It was hard to understand how they could have been shocked at first.  That is, until it was discovered that the negative buses of all the blocks were connected and if one was energized, then all the others were too. The commissioning team had been told not to work on the area where the employee was working, but could energize parts of the block. There was a human error in communication of this coordination, and the commissioning team wasn't aware that employees were working in an area that could be affected by energizing other areas, and therefore energizing the negative buss of the employee's area. That was an unfortunate mistake. 


In this case, human error contributed to the issue, but it wasn't the cause of the shock. The cause of this electrical shock was not following NFPA 70e and our electrical program designed to prevent injury and electrical shock when human error happens. The electrically safe work condition.

In NFPA 70e, an entire article is dedicated to establishing an electrically safe condition when working on any circuit or piece of equipment after the building or project has been energized and connected to the utility service.  Project team members followed most of the steps for an electrically safe work environment in this case, identifying sources of power, disconnecting, and placing Lock Out Tags properly. Despite the team's efforts, there was a human error which made Lock out Tag Out ineffective.  


Before performing any work on any equipment, NFPA 70e also requires that we perform a live dead live test with a rated meter to ensure that there is no voltage present. Until we have done this, we are not in an electrically safe working environment.  According to the installation plan given to the employee, there was no requirement to perform a live or dead live test to ensure that the circuit and load break were de-energized. This test was not mentioned in the JHA and JHA briefing for the employee. Before beginning the work, no one thought to ask the employee if he had a meter to perform a live dead live test or to test the circuit or equipment. 


If this simple step of testing it before the work was done had been done, it would have been discovered that the negative bus was live and the work could have been stopped, the human error in coordination would have been discovered and corrected and no one would have been shocked. 


Fortunately, there were no serious injuries in this incident. In the future, that may not be the case and someone could be seriously injured or killed. How many times have you worked on a box, fixture, or piece of equipment that was energized in a building without performing this test to ensure the circuit was de-energized? Based solely on the fact that things were locked out, people had informed you it was not energized, or your belief that it couldn't be energized. 


Human error cannot be eliminated. No one is perfect. Despite our best efforts, mistakes will happen. There are many things that can go wrong that can expose you to electrical shock when you shouldn't be, such as a leak in the circuit, or something that was locked out that didn't de-energize the thing you're working on.  The only way to prevent this is to understand NFPA 70e, to reference it regularly and to apply it, as well as to always, always, always ensure we are working in a safe electrical environment and to always ensure that the work we are doing is de-energized with a rated meter to ensure there are no voltages.





Yours and everyone you work with lives depend on it.

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