Priest Rapids Dam Arc Flash Explosion (2014)

An arc flash explosion occurred at the Priest Rapids hydroelectric dam in Eastern Washington leaving six employees injured of which, two of them were critically injured.

The employees were attempting to troubleshoot the circuit breaker on P08, which was one of ten generators at the dam. The repair work to the generator was not on the regular work schedule, and as it was towards the end of the work day, certain safety precautions were bypassed. The assumption was made that the power was cut off to the circuit, but it was never verified.

The circuit breaker was manually slow closed while energized with generator unit P08 in a stopped position. This caused an arc within the breaker, resulting in an explosion.

What should be done to avoid such incidents in the future:

To ensure safety of your employees and electrical infrastructure it is advised to get the following tests done:

Further, only qualified personnel with the proper training should work on electrical equipment with appropriate electrical safety garments and tools.

https://www.ecmweb.com/safety/accidents-investigations/article/20901585/hydroelectric-dam-explosion-injures-utility-workers

https://www.powerstudies.com/blog/what-caused-priest-rapids-dam-arc-flash-explosion

https://columbiabasinherald.com/news/2015/nov/08/arc-flash-declared-cause-of-priest-rapids-2/

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