Polaris was engaged to evaluate damage to a 2000A bus duct at a multi-story commercial office structure in Texas.  The electrical service at the structure consisted of 2000A, 277/480V distributed through a 2000A vertical aluminum ‘Cutler Hammer’ bus duct.  Polaris observed that the bus duct was damaged. A hole consistent with heating of the duct wall and smoke signature were observed around the bus duct wall. Shrapnel was observed in the vicinity of the failed bus duct. Heat damaged insulation and four heat damaged bars were observed inside the bus duct. Based on the observations, Polaris determined that the damage at the bus duct was related to an arc blast.

An arc blast is one of the effects of an arc flash.  When a short circuit occurs, it can often cause arc blast, a type of highly dangerous electrical explosion.  Its explosive force can turn metal objects into high-speed shrapnel.

Polaris’s scope of work also included determining the cause of the arc blast.  Polaris’s electrical engineering experts did not observe any evidence of human error due to reported recent maintenance. Further, no evidence of buildup of conductive dust, dirt/foreign debris, moisture, or other conductive liquids, significant corrosion of electrical components, or animal contact (e.g., rodents, roach, spider) which would have caused or contributed to the failure of the bus duct.  Polaris obtained and reviewed lightning data on and around the date of failure, which indicated that no lightning strikes occurred.

In the absence of any other external event, Polaris’s electrical engineering experts determined that the arc blast at the bus duct was caused by age-related degradation.  The age of the equipment was reported to be approximately 30 years and aged/weathered conditions were noted by Polaris.  Polaris also provided repair recommendations which included removal and replacement of the bus duct.