The San Francisco International Airport (SFIA) has applied its inclination toward advanced technology to its power management system, linking state-of-the-art power meters and circuit monitors with software to monitor its power system. The PowerLogic system from Schneider Electric provides early notification of power system trouble and vastly reduces the labor required to monitor tenant electrical usage and produce bills. The system allows the airport to pass along all aspects of the electrical rate, including time of use and multiple tier energy and demand rates. It also provides detailed power usage information that the airport can share with tenants.

SFIA ranks as one of the most technologically advanced airports in the United States, providing customer conveniences such as wireless internet access and direct terminal access from the local rapid transit system. The airport had been using PowerLogic meters from Schneider Electric for several years. Staff electricians were impressed with the equipment's quality, yet over time they realized that new technology could expand the system's capabilities and help them achieve even greater efficiency. After studying alternatives, the airport standardized on advanced PowerLogic CM4000T, CM4000, and CM3350 circuit monitors for their medium voltage circuits. Most of the metering on the low voltage distribution system consists of PowerLogic power meters and Enercept meters. The power monitoring system data communications consist of RS-485 serial daisy chains at the device level that connect to EGX Ethernet Gateways in each electric room. The system uses Ethernet, both fiber and copper, to bring the data to the server that runs the PowerLogic System Manager software.

The higher end circuit monitors are used to track/manage power quality on all mains and medium voltage circuits. The circuits feeding tenants who use less power-including restaurants, gift shops, and coffee houses-use PowerLogic Power Meters, which provide high accuracy, in-depth metering information from a small, easy-to-install unit. Even smaller loads, such as jetways, are monitored with the PowerLogic Enercept meter. The Enercept meter consists of a set of three smart split-core current transformers that can be easily installed on circuits inside electrical panels without modifying the panel.

When purchasing new power equipment, the airport now specifies electrical equipment with instrument transformers ready for connection to the meters, which are installed on new equipment regardless of brand.

“We're finding that the newer equipment, especially the CM3000s and CM4000s, are very flexible and allow for a lot of controls,” said Jim Wolanin, airport electrician supervisor. “From one meter we can control 14 separate functions and the sampling rate is dramatically increased. That capability allows us to do power quality studies, complete with graphs, that are helpful when tenants report problems. For example, we can show the tenant where a problem actually arises, which in some cases is the utility or even the tenant's own equipment.”

The PowerLogic system tracks the status of the airport's165-megawatt (MW) capacity power system, which maintains a 40-45-MW load, leaving a tremendous amount of capacity for airport expansion. The airport is fed from many substations, with all critical loads being fed from two separate sources to minimize outages. The airport also designed for redundancy on the low-voltage side, with a system of main and tie breakers that allow loads to be fed from several different possible sources. The mains at each substation, as well as downstream circuit breakers, are equipped with circuit monitors and tied together through a fiber optic link. The power management system comprises more than 350 PowerLogic meters of various types, a Modicon PLC to monitor the 12-kilovolt (kV) system for abnormal conditions, and a SMS 3000 software engine with GFX interactive graphics and a Billing Module, all linked by the fiber optic cable backbone.

The system uses an advanced 12-kV distribution system alarm module that watches circuit monitors at high-voltage substations. It monitors bus loading and initiates alarms on the sudden variation of load from established norms; if kilowatts drop below a preset load level or if circuit breakers open, the airport's central control is alerted. This provides airport electricians with an early warning system that notifies them of facility electrical problems, ideally, before they're contacted by the tenant.

Airport facility management uses the PowerLogic system's advanced power quality and detection capabilities to demonstrate to tenants that specific power quality problems originated not within the airport itself but upstream at the utility system. This capability avoids undue labor to investigate such issues and speeds diagnoses of power quality problems.

“For example, recently the local utility lost some transmission lines, which caused some big voltage sags-we took three big hits. But we could document why the outage occurred and communicate that to our tenants-diffusing a potential problem,” Wolanin said.

The system's most fundamental benefit is labor savings-both in the number of electricians required to read meters and in the time required to do the work. “Ten years ago the airport was one third the size it is today,” Wolanin said. “It was then a full-time job for one person to read and service the meters. If we had not upgraded with the PowerLogic system we would need three people; instead we're saving more than $90,000 on labor.”

Airport electricians no longer have to expend time and shoe leather to manually take readings from each meter scattered throughout SFIA's complex of terminals, hangars, and other outlying buildings. That process used to include driving or walking to a remote location, through various security checks, and reading data from the meter every month. With the PowerLogic system, meter data are fed automatically to a central control room and is accessible by PC.

“We can read the meters remotely via PC, which is a great benefit, especially for the new, outlying hangars and buildings occupied by our larger tenants,” said Wolanin. “It's beneficial because it saves the time that would have been required to send technicians to those buildings to read the meters, and it allows us to track power factor demand, charges and surcharges, print hard copies and allow us to e-mail those bills to accounting; it speeds the whole cycle of reading meters and billing tenants.”

This advantage alone is significant because when the meters were read manually, the airport retrieved total energy use but couldn't capture time-of-use data. The rates the airport pays the utility however, include such things as time of use during peak and demand charges. That important information is now captured at each point through the system and provides another significant advantage to the airport. The system allows the airport to generate a bill based upon the same rate structure that the tenant would have if they were directly connected to the utility. This helps the airport by allowing them to pass along costs to the tenant that much more closely reflect actual power costs and also rewards tenants who conserve energy during high cost rate periods.

The most recent application of the PowerLogic System is performing remote switching operations through the System Manager Software interface. In the past, switching operations required driving to remote substations, unlocking gates and doors, and finally operating the desired breaker. This process had to be repeated several times until all circuits were configured as desired, which often resulted in hours long switching operations. The PowerLogic System now allows these same switching operations to be performed in minutes through the secure software interface.

Portions of the power management system were installed by electrical contractors, but for the most part the system was installed, and is used and maintained by SFIA electricians. Several electricians were trained on the system at Schneider Electric's PowerLogic University, and they use Schneider's technical support center for ongoing support as needed.

“This power management system provides better control, more and better information, and gives us the ability to act sooner and faster,” Wolanin said. “And in realizing the additional benefits from the PowerLogic capability we have gained insight for building a whole new electrical distribution system.”