Forensic Engineering Analysis of a Sequence of Power Infrastructure Failures Atop an Office Building

Abstract

A series of equipment failures occurred in a high-rise office building in Puerto Rico. The top 18th floor was occupied by the infrastructure systems of the building to include heating, air conditioning, electrical and plumbingsystems, and two 1,500kVA emergency generators that provided power for the entire building when the utility power was not available. The first failure occurred within a 3,000kVA, 13.8kV/480-277VAC stepdown power transformer on a Sunday night — a day after the annual maintenance of the electrical equipment took place. Thefailure of this transformer resulted in the operation of the two emergency generators — last maintained a month earlier. The second failure occurred in one of the two control panels associated with the fuel day tanks for the emergency generators due to power disturbances (harmonics) in the electrical distribution system in the building. This resulted in an overflow of fuel oil in one of the day tanks (615 gallons) and the spill of approximately 1,000 gallons of fuel oil on the 18th floor and lower floors (including the cellar).