ORLANDO, Fla. - The Orange County Convention Center, recent home of the International Air-Conditioning, Heating, Refrigerating Exposition (AHR Expo), seems to be in constant expansion mode.

The latest Phase-V expansion project consisted of 2.8 million square feet of exhibit and meeting space. To make sure the new addition has a reliable supply of standby power, the general contractor, Hunt Construction Group Inc., turned to Cummins Southeastern Power for an "unconventional solution."

While all phases have their own standby power systems, Phase-V is an entirely separate structure with its own standby power system about a half mile from the Phase-V building itself. Generators are connected by a high-voltage underground power line (15 kV) to minimize line loses. Communication with the 72 automatic transfer switches is carried out over fiber-optic cables. The system's PowerCommand® digital master control also communicates with the building management system (BMS) for various operations and maintenance functions.

Backups

The standby power system in the Phase-V expansion consists of four 1,500 kW diesel generators along with controls, switchgear, and automatic transfer switches. The 6-megawatt standby power system is designed to provide backup power for all of the lighting in the complex, ventilation fans, refrigeration in the four food service courts, elevators, and security systems in the event of a utility power failure.

The standby system is one of several layers of power redundancy built into the Phase-V facility, partially in response to lightning, hurricane, and tropical storm dangers. According to Brian Kennedy, assistant HVAC supervisor at the convention center, when Hurricane Charley passed over Orlando, the Phase-V complex did lose main power. At that point, the new standby power system came on and operated as designed for several hours, he said. "Anytime the automatic transfer switches sense a power loss from any of the 11 utility feeds, they send a signal to start the generators," he said.

When a power outage occurs, all four 1,500 kW generators start and come up to operating speed in about eight seconds. The first generator to reach speed and proper frequency closes with the main bus. If one or two generators are sufficient to carry the emergency load, the other two generators shut down automatically and return to standby mode. When normal utility power is restored, a signal from the automatic transfer switches sends the generators into a "cool-down" mode before shutting them down. With 10,000 gallons of diesel fuel on hand, there is enough fuel to power all four generators for 24 hours.

Publication date: 02/21/2005