Currently ranked fifth worldwide for passenger convenience among airports with over 25 million passengers, the Minneapolis-St. Paul International Airport is in the midst of a major expansion project that, when completed in 2004, will accommodate 40 million travelers. Maintaining this high level of service is a priority. But as the airport grows, so does demand for the electrical services that keep an airport functioning smoothly. Boilers, chillers, heating, cooling and ventilating systems; security cameras, monitors, and computers; elevators, lights, public address, commercial operations, and more all rely on uninterrupted electrical service.
To ensure continuous service even during an interruption of electric power, the airport has installed a new standby power system for the airport''s Lindbergh Terminal, seven concourses, roadways, and parking ramps. Engineers designed an efficient on-site system that relies on the PowerCommand® pre-integrated standby power system from Cummins Power Generation. Rated at 6 MW on a standby basis, the system includes four 1500 kW PowerCommand generator sets, PowerCommand network, and PowerCommand digital paralleling equipment.
"While the primary function of an airport standby generator system is to provide power for life safety systems, these units give us the dependability and performance to provide essential operations now and when the expansion is complete," said Bob Tschida, project engineer, Dunham & Associates, Minneapolis. "In the unlikely event of a power failure, the standby generator will power the exit lights and fire alarms needed to direct people safely out of the buildings. More than that, the system provides standby power so the airport can maintain a basic level of operation during a power interruption."
Although the airport''s redundancy system virtually guarantees uninterrupted utility power -- three different utilities service the airport -- operating without standby power is unthinkable to airport officials. Without essential services to keep flights arriving and departing on time, a domino effect would topple operations at other airports as well. "We would have to close down the airport if we didn''t provide essential operations such as heating, cooling, ventilating, lights, security cameras, and surveillance, not to mention commercial operations," said Tschida.
The airport''s fiber optic hub and the "smart" technology of PowerCommand''s integrated digital control allowed designers to install an efficient system -- despite the networking obstacles posed by the length of the 2,000 ft concourses.
The PowerCommand power system from Cummins Power Generation provides an integrated system of generator sets, transfer switches, paralleling equipment, and controls to coordinate all the demands placed on an electrical system. These components are designed and manufactured to work together interactively. PowerCommand power systems feature "smart" components that can communicate with one another and facilitate remote monitoring and control along with the PC network. This feature improves functionality, enables easier installation, and reduces operating and maintenance costs, according to Cummins.
"Our challenge was to provide an efficient, integrated system over the length of the concourses," said Chris Hoglund, electrical engineer, Cummins North Central. "By tapping into the airport''s fiber optic communications system, we were able to eliminate the cost of running thousands of feet of wire. Plus, the networking ability of the PowerCommand system allows us to communicate a lot of information over long distances."
In the airport''s main generator control room, a PC-based control console monitors the status of 30 automatic transfer switches, allowing engineers to control and segment the load to distribution panels located throughout the airport. Gateway modules convert data on twisted pair into fiber optic signals to allow monitoring and diagnostics at remote locations thousands of feet away. Eleven routers located throughout the airport, and monitored from the main control room, provide overall control of the transfer switches.
PowerCommand provides an important maintenance function over the network even while the generators are not operating. From the control console, technicians can monitor the actual power consumption in each area of the airport. If a current load is lower than normal, they know something is wrong. "We can identify a trouble spot before it''s identified by the user," said Tschida. "This feature provides unlimited capability for maintenance."
Although the standby power generator system will be exercised monthly, it is seeing more regular use during the current construction project. While utility service upgrades, the generators provide the airport''s electric service. "We occasionally need to switch off our power from the utility. Switching to the standby generators lets us continue construction without inconveniencing the airport," said Tschida. "The standby generators play an important role in providing uninterrupted service even during construction."
When there is a loss of utility power, PowerCommand power system senses it, and starts all four generator sets after a 3-second delay. The first generator set that gets up to rated speed picks up high priority loads. The remaining three generator sets synchronize to the generator bus and as they connect, additional loads are added to the system. The entire startup and synchronization sequence takes less than 15 seconds. All four generators run for 15 minutes, after which the system analyzes actual load requirements. If the load can be handled by fewer generator sets, PowerCommand automatically shuts down the unneeded generator sets. If additional load is added to the system, PowerCommand automatically reconnects required generator sets. When utility power is restored, the generator system will continue to run for a selected stabilization period. Once utility power remains steady throughout this period, load is re-transferred back to the utility.
Although the generators provide a critical function for airport operations, the equipment is designed to be unobtrusive to the traveling public. Engine noise does not exceed the airport''s normal ambient sound levels. Because the generators are located underneath a busy public concourse, exhaust silencers and sound attenuation baffles ensure low sound levels when the generators are running.
Keeping 40 million people traveling throughout a busy airport without incident requires careful engineering and organization. Thanks in part to the PowerCommand standby power system, travelers will continue to benefit from the safety and security that gives the Minneapolis-St. Paul International Airport its reputation for passenger convenience.