Know all the causes of arc flash accidents
Are careless employees always to blame?
Areview of the literature on the causes of arc flash and other electrical accidents most often points to worker carelessness as the number one problem.
“Carelessness” may be too broad of a generalization. Fatigue or being pushed to quickly restore power by supervisory personnel is not pre-meditated carelessness. In general, too many accident investigations of all sorts often “take the path of least complications” and point the finger and blame at the worker.
In addition to worker behavior and attitudes, many types of problems with equipment cause arc flash accidents: worn or broken conductor insulation; exposed live parts; loose wire connections; improperly maintained switches and circuit breakers; obstructed disconnect panels; water or liquid near electrical equipment; high voltage cables; static electricity; and damaged tools and equipment.
Operational system or working culture issues often fail to find equipment problems or correct at-risk behavior. Both OSHA and NFPA 70E require an electrical hazard analysis prior to beginning work on or near electrical conductors that are or may become energized. Results of the analysis will determine the work practices, protection boundaries, personal protective equipment, and other procedures.
But the findings are not always relayed to the workforce. “There are too many workers unaware of danger of working on live electrical equipment,” said one electrician. “Electricians working for small size companies have no idea what danger is lurking inside the electrical enclosures.” The main factor that influences the available arc flash level is the upstream source and the upstream protection. How correctly is the analysis performed and protection devices set up?
Other system failures that can lead to accidents:
- Ground-fault relays are not included in a preventive maintenance program
- Non-compliance with the requirements of NFPA 70 for ground fault protection, which requires detectors for some specific applications of ungrounded electrical systems.
- Failure to implement formal work controls for working on ungrounded delta systems that could have a ground fault.
- Arc flash calculations for the building where an incident occurs are not completed and warning labels are not posted.
- Pre-job briefings are not held
- Personnel do not stop work when they observe an electrical engineer not wearing proper PPE
- The OSHA required (29 CFR 1910.132 - PPE) hazard assessment requirements for breaker installation are not conducted.
- An employer’s practices regarding working on or near energized electrical equipment violate OSHA standards
- Frequent mistakes are made in calculating safe working distance. If a larger than normal working distance is used, it can give a false sense of safety. Also, working distance appears to be a simple concept until you attempt to determine the location of the possible source of the arc. The working distance generally assumes the energized conductors are located near the rear of the equipment, but that may not always be true.
One man’s story
The testimony of Donnie Johnson on his website, www.donniesaccident.com, says all there needs to be said about the combination of worker carelessness and faulty equipment. On August 12, 2004, he was connecting large electrical generator in preparation for a hurricane in Florida. The meter he was using failed and blew carbon into the gear and created an electrical arc which resulted in an arc blast. Johnson ended up with full thickness, 3rd degree burns to both hands and arms along with 2nd and 3rd degree burns to his neck and face. He was in a coma for two months due to numerous complications from infections and medications.
Said Johnson, “All of this happened to me, because I wasn’t wearing my safety gear. If I had been wearing the personal protection equipment that was provided for me, that I was trained to use and still in the PPE bag between the front seats of my van; my trip to the hospital would have probably been just for a check-up and a few, minor burns.”
At the point of the job when Johnson had the wiring in place and terminated, he said, “This is the point where I should have pulled out my fully stocked PPE bag. But I did not, due to having performed similar tests many times before and thinking ‘what could possibly happen as long as I am careful’ and ‘all that gear is so hot and bulky’.”
The meter he had been using for several months to check rotation was not actually a phase rotation meter but a motor rotation meter. Johnson had never bothered to read the “not to be used on live circuits” label on the bottom of the meter.
When someone complains about the safety gear being hot, uncomfortable or too bulky, Johnson pulls up his sleeves and tell them “it’s a hell of a lot more comfortable than living with this for the rest of your life… If you make it.”
OSHA enforcement reports show inspectors will cite employers for not anticipating or correcting human error. In one case a utility was cited because a crew leader did not conduct a hazards briefing before work started the morning of an arc flash accident, and also because crew members failed to wear all recommended protective gear. Two workers did not wear long-sleeved shirts, and one who did had the sleeves rolled up and was injured. Only one employee was wearing a face shield attached to a hard hat, but he did not have it swung down to protect his face.
“We go over this stuff. The safety programs are there and in place, but their guards were down for whatever reason,” said the utility manager, who guessed that perhaps the heat or the fact that it was a Monday morning may have contributed to the missteps.