Power quality evaluation at medical center

A power quality evaluation was conducted to determine (i) the cause of nuisance tripping of electrical equipment at Baptist Medical Center in Little Rock, Arkansas and (ii) whether there was any correlation of these nuisance tripping events with voltage sags on the utility system as a result of source-side faults. The facility's total connected load exceeds 6.5 MVA. The interruption of the facility's large chillers and associated air-conditioning equipment, as well as computer and critical diagnostic equipment were of particular concern. This paper describes the different stages of this power quality evaluation which included: (i) an on-site inspection of the facility's;'s electrical system, (ii) continuous power monitoring at the medium-voltage service entrance and at the utilization voltage buses of sensitive electrical equipment in the facility, and (iii) an evaluation of the applicability of a medium-voltage high-speed static source transfer switching system.