Transformer Incident (KV187v2)


What Happened?

On February 2nd 2019, an employee was energizing a padmount step-down transformer for an industrial customer.  After inspecting the transformer to ensure all wiring had been terminated and the T-switch was placed in the closed position, the outer doors to the transformer were closed by the employee. And, the transformer was energized by closing the disconnects at the dip pole. 

Customer employees were on site, and when the transformer was energized, they left to check voltage on their equipment a short distance away.  Once at their building, a loud boom was heard.  They saw that the employee had sustained injuries and went to render aid.     

During the Safety Event team’s work, it was noted that the Company employee had reopened the cabinet door (4160V side) to the transformer.  A voltage meter was also observed at the base of the cabinet and had received major damage. 

Contributing Factors

The transformer was received without the required inner barrier per Company Standards.

This is an infrequently performed task.

There was a lack of hazard recognition – the cabinet door was clearly marked with the appropriate information regarding voltage and warnings.

What Can We Learn?


Since this was an infrequently performed task, the worker could have used a Self-Check (STOP (Stop, Think, Act, Review)) to ensure he was focused on the task and all the information was gathered prior to starting work.

The employee could have used a Questioning Attitude to question every aspect of what he was doing and to ensure he was fully aware of the situation before proceeding. This would have been helpful in questioning if the transformer was up to Company Standards prior to work starting.


He fell into the Overconfidence trap by underestimating the risks involved and overestimating his competency in completing an infrequently performed task.

The employee might have been Distracted since Company’s customers were on site and examining the work.    

Ask the Right Questions

How does this relate to our work?

Where do we have similar traps?

What Tools can we use to avoid a similar incident?

Was a stop work point missed?