Thanks for the feedback, all possibilities.
Vibration is possible although this substation is fairly remote on the facility (fenced it). Moisture could explain the irregularity of this event.
With regards to a DC transient, that is actually the path that I originally started down, and I'm...
I was hoping to get some in input on potential root causes for the activation of an 86 lock-out relay specifically used for a breaker failure feature (referred to as 86BF on the attached drawings). We took down a large portion of our facility due to the activation of this 86BF that I found to be...
