RE Magazine

May 2012 

FNET: Taking the Grid's Temperature 

 

 

New Research Could Make Power Network Monitoring More Feasible

The electrical grid is in a constant state of flux. Loads rise and fall. Generators malfunction and trip offline. Tornados and earthquakes take transmission towers out of service. How do these events affect the overall health of the grid? Which of them could trigger a widespread outage due to voltage collapse or transient instability?

It's possible to monitor grid health by capturing frequency, voltage, and phase angle readings using phasor measurement units (PMUs). But PMU data must be analyzed from many points over a wide area. And with a price tag that can be more than $80,000 per unit, the cost of deploying an adequate number of sensors can be prohibitive.

But researchers at Oak Ridge National Laboratory (ORNL) in Oak Ridge, Tenn., and the University of Tennessee, Knoxville, (UT) may have found a more cost-effective solution. Teams there are currently experimenting with a wide-area measurement system dubbed FNET/GridEye, which employs devices called frequency disturbance recorders (FDRs) to provide a subset of PMU data.

Developed at Virginia Tech, FDRs are similar to single-phase PMUs and are inexpensive and easy to install. The devices being used by ORNL and UT connect at 120V (instead of the higher voltages used by PMUs), meaning installation is as simple as plugging into a standard wall socket. They use GPS signals to synchronize measurements, and data is transmitted to servers located at ORNL and UT via the Internet. (See video at right.)

The teams are able to create powerful graphic visualizations of system events (see videos at right) and are developing tools and techniques that will manipulate FDR data to give a continuous, real-time picture of grid performance.

Because frequency fluctuations can be a bellwether of impending severe grid instability, monitoring provided by FNET may one day be helpful in avoiding widespread outages. In addition, FNET data can be used in system simulation programs that could predict impending voltage collapse—the major source of system outages and blackouts.

Looking for co-op partners

ORNL and UT are looking for utility partners to help test FNET/GridEye nationwide and have turned to NRECA's Cooperative Research Network (CRN) for help identifying electric cooperatives to participate in the ongoing study.

"Currently, we have approximately 80 monitors deployed across the United States," says ORNL researcher Marcus Aaron Young II. "We would like to increase that number to at least a few hundred distributed across the three North American interconnections."

Project funds typically cover the cost of the monitor; host co-ops need only commit a few minutes of their time for the installation and will have access to the data from their monitors.

Co-ops interested in hosting an FNET device should contact CRN's Debra Roepke at debra.roepke@nreca.coop. More information about FNET is available at the FNET website.

FDRs use GPS signals to synchronize measurements, so access to a window is required. And data is transmitted to servers via the Internet, so a network connection is a must. But the entire installation process takes only a few minutes.



A tripped generator in Florida in 2008 sent ripples of frequency fluctuations as far north as Minnesota and Maine. Title: Earthquake (2011)



The earthquake that hit the Mid-Atlantic States in 2011 caused frequencies to plummet throughout the eastern U.S.



A severe storm in 2011 set off waves of frequency instability in the Eastern Interconnection. Title: Florida Generator Trip (2008)