Investigation and Root Cause Analysis of Transformer Metering Destruction by Arc Flash

An arc flash and fire in the secondary compartment of an industrial facility utility transformer resulted in destruction of newly installed electrical metering equipment. Inherent to this type of event are two loss-of-evidence challenges: extremely high heat burns or melts everything nearby, and urgency to restore normal operation may prevent comprehensive examination of the scene. The facility contractor’s operations staff conducted an initial root cause analysis. The contractor’s management called on an external forensic team to provide an independent assessment. Having an established investigation methodology allows the forensic examiner to better understand what was, and was not, evaluated by facility staff and prevents confirmation biases. This paper examines the facility’s report, addresses shortcomings in its conclusions, and goes on to detail the methods and reasoning behind the forensic team’s findings. The methodology presented in this paper is applicable to a wide range of industrial electrical fires.