Healthier Power for Expanded Hospital
By Staff -- Consulting-Specifying Engineer, 12/1/2003
When officials at the Audubon County Memorial Hospital in Audubon, Iowa, completed the facility's recent expansion, they soon realized they had neglected one vital element. Although power requirements at the 25-bed hospital had grown to 375 kW, their existing emergency standby generator could only supply 175 kW of electricity. This meant leaving some non-critical systems unprotected in the event of an outage or disruption, to ensure life-safety functions would not be compromised.
Required monthly tests of the equipment were also proving problematic. The hard transfer from utility to generator supplies caused a 3/16th of a second outage, which was enough to disrupt some clocks, lights, computers and security devices. As a result, maintenance staff had to alert all personnel prior to testing to ensure computers were backed up and other needed preparations were made.
To meet both supply and testing needs, facility managers decided a new generator system was in order, along with a load-transfer solution that addressed the brief outages they were experiencing when switching to generator power. Although they initially considered a 250-kW system, which would have met emergency-supply requirements, a utility demand-side management program provided the necessary financial incentives to think a little bigger.
The hospital installed a 600-kW diesel generator set that allows them to participate in a load-shedding program established by the local electric utility. Not only is the hospital fully protected in case of outages, it also is able to quickly separate itself from the grid up to 16 times a year during summer peak periods. This latter capability earns the hospital up to $11,000 in savings annually.
To ease the load's transition from utility to generator, the hospital included a soft-loading transfer switch in its plans. With this design, the utility and generator operate in parallel for about five seconds as load gradually shifts from one system to the other, eliminating the voltage and frequency dips of the previous hard-transfer scheme.
