Voice of Experience: Human Performance Failures
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I find human performance a fascinating topic to teach during my supervisor training classes. Many readers of Incident Prevention are familiar with the topic. For those who aren’t, human performance is an analytical tool that examines how people accomplish tasks and why they perform those tasks in a particular way. Employees in the electric utility industry execute many of the same tasks each day. We do them according to the local culture’s work practices, primarily learned through on-the-job training. As older workers retire and new employees join the ranks, those work practices are passed down to the next generation. Sometimes the practices are not the safest approach and can lead to incidents and accidents.
At one point in our industry’s history, it was common to blame employees when incidents and accidents occurred, but we have learned over time that human error rarely is the root cause. That’s where human performance tools help employers identify and correct latent organizational weaknesses and errors. A company that invests in human performance analysis can minimize active errors on their job sites. Human performance training helps employees understand risk adversity, particularly how the coincidental experience of an injury-free work history can cause increased risk and exposure to an employee simply because nothing bad has happened to them so far. Workers can become so used to risky practices that they often will assume they’ll be alright today and in the future.
Human Performance Failure: Case 1
I want to share with you two incidents in which human error played a role but was not the root cause. In the first case, there was a flash but no injuries; in the second, a serious injury occurred after a worker made a phase-to-ground contact. Both cases involved orders to completely switch out a substation to perform maintenance on switchgear. In each case, the basic requirements found in OSHA 29 CFR 1910.269(m), “Deenergizing lines and equipment for employee protection,” were followed, but one switching order – which had been written, reviewed, dispatched and executed by field employees – was missing a vital step that led to an employee making an error.
In the first case, a substation with eight distribution circuits was scheduled to be switched out for maintenance. Switching orders were written by engineering staff, reviewed by other engineers and dispatched by a system operator. Employees executed the orders as dispatched, without question. All eight circuits were switched out. Seven of the eight circuits were completely cleared, isolated and grounded at the station frame.
The load on the eighth circuit – a three-phase UD cable feeding from the station frame to a UD termination riser pole – was switched and the breaker was opened. The opening, tagging and grounding steps for the 800-amp riser pole switches were left off the switching order. The switches were left in the closed position and were feeding back into the station from the UD riser pole just outside the fence. They were in clear sight of the breaker looking toward the fence. The scheduled work proceeded in the substation until sometime later. About two days into the outage, an employee was in the bay working near the ungrounded circuit and realized grounds had not been installed on the eighth circuit. The employee proceeded to place a ladder on the frame and attempted to install the grounds, which resulted in a phase-to-ground flash. He had never checked for the presence of voltage with an approved voltage tester. The switching order had been written by highly trained and experienced engineers and executed by highly qualified and experienced personnel. Still, no one noticed that the testing and grounding steps had been left off. Further, the flash could have been avoided simply by verifying with a voltmeter that the circuit was energized.
Human Performance Failure: Case 2
The second case is similar to the first because it involved completely switching out and de-energizing a substation that had four distribution circuits. In this case, a contractor was employed to make repairs to the transfer switches after the station was switched out. All load was transferred off the four distribution breakers, and all line and load switches were opened to isolate the breakers from system voltage in the station. The owner of the substation requested that the transmission company de-energize the station power transformer, isolate it from the bus, check for absence of voltage and ground the distribution side from the power transformer.
A written clearance had been established, extending from the transmission circuit to the load switches on distribution breakers. The switching clearance had been completed and was then assigned to the contractor company performing the work. Because the owner of the distribution circuits failed to de-energize the circuits back to the frame, this allowed primary voltage back to the frame and up to the load side of the transfer switches on all four circuits. The contractor only had one employee, who was qualified per OSHA 1910.269(a)(2). He was assigned the clearance, and it was communicated by the owner of the station and the operator of the transmission line that there was no voltage in the substation. No one checked the load side of the station breaker disconnects for absence of voltage. A contract employee in a non-insulated aerial lift attempted to grab the load-side switch blade of the transfer switch, which was energized by the backfeed into the station. This resulted in a phase-to-ground contact with severe injuries.
In both of the cases described above, the failure of the employees in charge to follow the OSHA standards resulted in flashes. Severe injuries also were sustained in the second case. Failure to manage the processes and all work as required by OSHA regulations is an organizational weakness that, in these cases, enabled employees to make active errors. Both of the incidents I described would have been avoided by following 1910.269(m), but trained and qualified employees failed to follow what are recognized across the industry as mandatory procedures as well as OSHA rules.
Human performance analysis used in audits of work practices and training helps to identify risky work habits and practices, both of which contributed to these incidents. People make mistakes, and human performance analysis helps us identify why mistakes occur and who is likely to make them.
In the electric utility business, we can never assume things are the way they should be. Employees must always verify system configurations and conditions and never assume anything without verification. Risk drift occurs as a result of experience or is innocently accepted by non-qualified employees who are unable to recognize hazards. Human performance analysis works to fix that.
About the Author: Danny Raines, CUSP, safety consultant, distribution and transmission, retired from Georgia Power after 40 years of service and opened Raines Utility Safety Solutions LLC, providing compliance training, risk assessments and safety observation programs. He also is an affiliate instructor at Georgia Tech Research Center OSHA Outreach in Atlanta.