Mission critical power backup

Hospitals require extraordinary reliability from their emergency backup power systems. Not only must all critical life-support systems remain online if the utility grid goes down, any other systems that could affect those operations also must be covered. And, with today's increased reliance on computerized medical records, data access is joining the list of essential services.

By John Meuleman, Russelectric Inc., Hingham, Mass. November 1, 2008

Hospitals require extraordinary reliability from their emergency backup power systems. Not only must all critical life-support systems remain online if the utility grid goes down, any other systems that could affect those operations also must be covered. And, with today’s increased reliance on computerized medical records, data access is joining the list of essential services.

One upstate New York healthcare system is leading the way in backup-power design, and is paying for it, in part, through demand-side management incentives.

Bassett Healthcare, based in Cooperstown, N.Y., has more than 270 physicians on its payroll and several physical plants on its balance sheet. The group operates a teaching hospital, a research institute, and a network of regional clinics that serve eight counties in its upstate region. And all of its 24 facilities are protected by emergency backup power systems that go beyond the capabilities of those of most other hospitals.

The value of these investments was proven in August 2003. During the blackout that affected eight states and parts of Canada, Bassett was an island of light in a sea of darkness, thanks to its emergency-power planning. The company’s flagship facility, the 180-bed Mary Imogene Bassett Hospital in downtown Cooperstown, played a key role by feeding the community, accepting refrigerated vaccines from county offices that had lost power, and providing other services for competing healthcare institutions that didn’t have backup power.

Since the blackout, Bassett has taken steps to expand its system’s capaibilities. A 2004 upgrade/expansion has added generating capacity and programmability. These improvements also help address the lack of a second utility-power source. Many healthcare facilities are located in communities with a second source of normal power, and some may be served by two electrical utilities. In fact, the NFPA code sees this as the ideal, stating: “For the greatest assurance of continuity of electrical service, the normal source should consist of two separate full-capacity services, each independent of the other,” (NFPA 99 2005 ANNEX A.

Lacking a second utility power source, Bassett depends on its backup generators to provide a power cushion in any emergency situation.

“Power outages are common,” said Joe Middleton, Bassett’s vice president for corporate support services and planning. “But it’s not just a reliability issue; it’s a matter of system redundancy—we’re in a rural area with a single electrical feed and no natural gas service, so it became necessary to create our own secondary power source.”

Bottom-line considerations

Bassett employs 2,800 people, more than the population of Cooperstown, and sees about 1,000 outpatients each day on top of regular admissions. While management’s first concern is how to provide the best patient care, reliable backup power has a fiscal benefit as well. Middleton estimates the loss of power for eight hours could cost the company up to $1 million in lost revenue. This financial impact was one driver behind Bassett management’s decision to create a backup system significantly stronger than codes demand.

The NFPA’s National Electrical Code (NEC) requires hospitals to maintain a base level of backup protection and to provide emergency power to loads supplying critical services for life safety, along with the HVAC system and some other equipment. Bassett’s immediate-response system also ensures that all elevators keep running. And then, 5 minutes after the beginning of an outage, two additional generators ramp up to restore full power to the hospital and 15 other buildings.

In an operating room, for example, this can make a big difference. The NEC requires only a certain percentage of electrical receptacles in these highly computerized spaces be served by emergency power. However, at Bassett, all receptacles are live after any initial, 5-minute outage. At that point, all the company’s facilities are energy independent, generating all their own primary power. The system can back-feed and feed around any fault on the campus.

Another backup system, entirely separate and distinct, ensures a continuous power feed to Bassett’s data center, located on the Cooperstown campus. This system, which has its own redundancies, allows no power interruptions at all. Such coverage is critical in today’s medical environment, in which the loss of computer access to patient drug histories, digital radiology films, and other electronic records would be a serious setback for doctors, nurses, and, ultimately, patients.

Middleton was an advocate for the extra backup he brought about at Bassett, and said, “As healthcare technology becomes more and more sophisticated, concurrent with the increased focus on expense control, the continuous delivery of medical information is critical. A reliable power system really needs to be a bottom-line calculation. Unfortunately, most healthcare facilities have not realized this yet.”

A history of improvement

The effort to upgrade Bassett’s power system has been a long one. It began in 1990 and 1991, with an initiative to design, build, and install switchgear synchronizing three 900 kW, 480 V generator sets for the main campus in Cooperstown. Upon loss of utility voltage, this still-operational system starts and synchronizes the three generator sets, and automatic transfer switches transfer the emergency load to the generator source. Upon return of utility power, after a time delay to ensure the utility source is stable, the transfer switches re-transfer the emergency loads to the normal source.

In 2004, Bassett upgraded the controls of the original paralleling and transfer gear and added two medium-voltage gensets (2 MW each), capable of generating 12.47 kV. Installed on a primary bus, these are linked to, and parallel with, the three original gensets.

With these upgrades, if the normal utility feed is not restored in 5 minutes, the new equipment switches to the Bassett system as the primary power source. Special controls in the paralleling switchgear and transfer switches lock the equipment in the emergency position, so it doesn’t roll back to normal. Then, when a tie breaker is closed, the system begins back-feeding through a 2,000 kVA transformer (480 V secondary, 12.47 kV primary) to generate enough primary power to feed the entire Cooperstown campus.

“In a sense, we’ve spoiled people,” said Middleton. “Our employees have become accustomed to continuous full power; they become very anxious with any transient outages. We’re seriously considering adjusting the timing circuit to reduce the delay from 5 minutes to just 2 minutes.”

When the normal supply voltage returns, the system, after a preset time delay, transfers all building loads, in the selected transition mode, back to the normal source. This retransfer sequence occurs in two stages. In the closed transition mode, the 12.47 kV generators synchronize with the utility power source, close the 12.47 kV utility breaker, transfer the load gradually to the utility source, and then open the 12.47 kV generator tie breaker. Once the 12.47 kV generators have transferred their load, the switchgear controls allow the 480 V transfer switches to retransfer to their normal position. The engines will continue to operate unloaded for a cool-down period. All controls are then automatically reset, in readiness for the next operation.

Paying for itself 

The switchgear also can be programmed for baseload peak-shaving. Thanks to a lucrative agreement between Bassett Healthcare and the regional power company, Bassett’s backup power system pays for itself over time. This interruptible power contract gives the utility permission to drop Bassett from the regional electrical grid (with advance notice) during periods of peak demand. In return, the utility pays Bassett, at a rate much higher than what Bassett pays for its normal feed, for every megawatt Bassett generates while off-line.

“It’s great for us,” said Middleton. “We’re off the grid for a few hundred hours a year, mostly in the summertime, when the power we generate is of higher quality than what we get from the utility. It’s rock-solid, with stable frequency and voltage. But on the grid, with all the air conditioning demands, we see large switching transients as new power sources are switched in and out.” Bassett also has the capacity to export power to the grid, although they have never been asked to do so.

Middleton makes sure he has 45,000 gallons of low-sulfur oil stored on site for the generators. The two largest generators consume 280 gallons/hour when operating—6,720 gallons every 24 hours. With the three older, smaller generators operating concurrently, Bassett could burn 8,000 to 10,000 gallons of oil a day just to power the main campus. Bassett’s two newest generators, the largest ones, produce fewer emissions together than one of the original generators purchased in 1990. All of Bassett’s generators are rated and permitted for continuous use, if necessary.

Today, in addition to the main facility, every Bassett clinic has its own automatic transfer switch for backup power, for a total of 30 generators, in all. Middleton estimates that 16 transfer switches and one set of paralleling gear, all of which were installed almost 18 years ago, will last another 10 years.

Author Information
Meuleman is vice president of Russelectric Inc., which designs, builds, and services on-site power control systems. He has more than 30 years of experience in emergency/backup power systems for mission critical facilities. He holds a degree in electrical engineering and is a member of the IEEE, AEE, 7×24 Exchange, and NFPA.