Date of incident: September 2023
Notice of incident number: 2023189800005
Employer: Electric utility

Incident summary
At an electrical distribution substation, two workers were preparing to conduct maintenance work on a transformer. One worker climbed a ladder and then stepped onto the transformer. After he took two steps, a carabiner connected to a D-ring on his fall protection harness inadvertently contacted energized high-voltage equipment. An electric arc flash occurred, and the worker sustained serious electrical burns.

Investigation conclusions

Cause

• Breach of limits of approach to energized electrical equipment. A 25 kV bushing and a 138 kV bushing were both near the top of the ladder, and the transformer was energized. When the worker was climbing the ladder and stepping onto the top of the transformer, he breached the limits of approach (LOAs) for the energized bushings.

Contributing factors

• Failure to de-energize transformer. The work plan required the de-energization and isolation of the transformer before the maintenance work began. The work plan for the maintenance of the transformer did not require either of the two workers (a subforeman and an electrician) to access the transformer while it was energized.
• Failure to conduct pre-work safety meeting. The work plan required the use of an aerial work platform (AWP) for tasks on the de-energized transformer. The subforeman moved the AWP into the substation before climbing the transformer’s ladder. A pre-work safety meeting was required before the AWP was moved into the substation, to discuss the potential hazards associated with the work and the work area as well as the controls to address the hazards, but no pre-work safety meeting was held.
• Failure to follow safe work procedures. The employer’s safe work procedures and the work plan required the subforeman to ensure the transformer was de-energized and a pre-work safety meeting was conducted before the work began. In addition, the LOAs for energized equipment should have been maintained.

Other safety issues

• Ineffective security measure. The substation was enclosed with security fencing and a locked gate. In addition, the transformer’s ladder was equipped with a hinged security door that was secured with a padlock. When the door was closed and locked, it effectively controlled access to the ladder and energized electrical components on top of the transformer, permitting entry only to qualified electrical workers in possession of the key. However, the padlock had been left unlocked sometime before the day of the incident. The employer lacked policies or procedures to track the unlocking or locking of its padlocks.

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