Power monitoring helps a major airport to plan ahead
LaGuardia Airport is part of the Port Authority of New York and New Jersey's three airport complex, which includes John F Kennedy and Newark International. LaGuardia is the 19th busiest domestic airport in the US; 900 aircraft arrive and depart daily, carrying about 21 million passengers a year.
LaGuardia's ongoing $800 million makeover began in 1992 with the expansion of the central terminal. Four building-utilisation substations were upgraded, and transformers boosted from 1000 to 2000 KVA capacity. In addition a new west end substation was built with four additional 27 kV feeders coming into the airport.
Expansion also meant that a better understanding of the airport's present and future power needs was required. The Port Authority appointed Power Measurement Ltd (PML) to supply a PC-based remote power monitoring system for all new substation equipment. Expanding or upgrading the monitoring system is simply a matter of adding commercially available software, hardware and network components. This modular, non-proprietary approach simplifies upgrading and provides a cost effective way to incorporate the latest computer and communications technology.
Today 46 PML panel-mounted `smart' digital instrumentation packages both hard-wire and modem-connected to a remote PC master display station in the electrical unit continuously scan the airport's electrical distribution network.
The monitoring system's instrumentation, a mix of digital 3710 ACM and 3720 ACM power meters and 3800 RTU smart transducer interfaces, with preset alarms on a wide range of parameters, are polled by the software on the master display station's PC. All airport electrical distribution status is recorded on the PC's hard drive.
Electrical supervisors now have hourly readings of the entire system. They are able to see exactly where power is going, when power consumption is higher or lower and overall power trends. And they can balance feeders according to these parameters, keeping power factor up and harmonics down.
ConEd's incoming 27 000 V is distributed throughout LaGuardia at 4 160 V. Three feeders enter each substation; two preferred and one combination alternate with hydraulic switchgear. In the main substation, four 3720 ACM advanced power meters monitor the 4 160 V distribution feeders, and 20 3710 ACMs the lower 120/208 Volt hangar and 277/480 Volt terminal branch feeders.
PML's 3800 RTUs monitor the position of the hydraulic switchgear to show whether power is flowing through a preferred or alternate feeder. Flashing lights on the PC display station's screen alert staff whenever the switchgear automatically shifts between feeders.
The office display station gives Port Authority supervisors a global view of the electrical distribution system. "To know what's going on, we simply glance at the monitor," says Slochevsky. "We see current, voltage, power factor, demand which switches are open or closed everything we need."
If higher demand or a larger load than normal was experienced during the night, the system alerts the electricians when they start work the next day, and they will check the reason why with the responsible terminal. This keeps them aware of any changing demand for power at the terminals that may affect the forecasting of airport electrical loads.
Port Authority staff can also determine why the airport suffered a power sag the previous night. The master display station will show, for example, that ConEd `lost' a feeder, thereby putting a dip on the system, and it will show the time the voltage went down.
Monitoring system paid for itself
In the past, Port Authority electricians had to make daily substation trips just to read the meters. "Now, just by looking at the PC screen, we have all the metering feedback we need," says Slochevsky. He adds that the permanently installed system paid for itself in a year simply from the time saved in not having to take readings. "The monitoring system has been accurate and dependable."
By knowing lowest demand periods, the Port Authority can schedule feeder maintenance during the least disruptive time. The monitoring system also helps avoid problems when testing with circuits offline. If the electrical load rises too high on other feeders, additional switching can be done in the field.
The system is also a valuable tool in a power crisis, helping the Port Authority maintain control of electricity to keep the airport operating. A transformer fire in ConEd's 138 000 V distribution meant that LaGuardia faced a power shut-down.
The Port Authority worked closely with ConEd, and the utility was able to reroute electricity to keep the airport alive. Luckily none of the airport tenants was affected. "But we were carefully watching the monitoring system's minute-by-minute readings of each terminal feeder to make sure no one internally was drawing electricity that we didn't have," says Slochevsky. If the airport's electrical consumption had had to be reduced, the monitoring system would let electricians know which tenants to call by usage levels.
The Port Authority now has access to months of data valuable information that can be used to revise estimates of present and future airport power consumption and that helps determine future expansion needs. It is also interested in PML's new PEGASYS monitoring software that is compatible with existing series 3000 instrumentation. Running under Microsoft's Windows NT operating system, the new client/server software can significantly enhance the monitoring system's networking and data sharing capabilities. LaGuardia is well positioned to meet the additional power demands arising from the expansion programme, and to offer tenants a high quality and reliable electricity supply.