Electric Power Quality

During a normal half-hour series of scans, a CT scanner records
images on a microcomputer that also controls the scanner. As
often as twice each day, this hospital's scanner would shut down
before a series was complete. The recorded images were lost, and
the patient was subjected to a repeat of the entire series. Utility
personnel found one cause of the shutdowns to be momentary
power outages caused by trees brushing against utility distribution
lines. They corrected this by trimming trees. Another cause was
then found to be voltage sags that occurred when the hospital's
chiller started. An improper setting on the scanner's power
control was corrected, and this problem disappeared.