Moving grid operations from minutes to seconds
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In the last century, the electric power grid has grown from a system that served one square mile in New York into a highlycomplex interconnected system that serves all of North America.
Initially, individual local systems would connect to each other to share resources and increase reliability. Today, utilities rely upon that same interconnectedness to save money by shipping large amounts of power over long distances, pushing the system closer to its limits more and more often.
At Pacific Northwest National Laboratory, researchers are exploring how changes in the way the nation's electrical grid is operated can improve its reliability and effectiveness—lowering costs and lessening environmental impacts. The focus is on developing real-time tools and supporting their integration into operating systems. According to Rob Pratt, who leads PNNL's Electricity Infrastructure Operations (EIO) Initiative, there is a need for grid operators to see beyond the individual control areas within their purview. If operators understand what is happening on neighboring systems, they could more quickly recognize and address the potential impacts to the system they operate.
This need for "situational awareness" was a key finding following the East Coast blackout of 2003, where events leading up to the blackout could have been detected and corrected before they spun out of control. Once started, the blackout spread from Ohio to New York in only nine seconds.
PNNL's EIO Initiative focuses on improving situational awareness by collecting more and richer data from a broader area and developing tools that allow timely analyses and therefore quick and appropriate action.
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For example, data collected by a conventional SCADA (Supervisory Control and Data Acquisition) system currently are refreshed only every four seconds. It can be another four minutes before the data are analyzed and results are available to operators. "Operators don't know for four minutes or more if the news is good or bad," Pratt said. However, a new and more precise type of data called phasor data that are timestamped and synchronized could be shared with operators across the system 30 times per second.But as we all know, having data is not enough," Pratt said. "We will eventually have thousands of these data points available, but we need new technology, including advanced analysis and visualization tools, to know where and when to look—and what we should be looking for."
Researchers are applying data-intensive computing to the process used to reconcile data coming in from the grid and the underlying fundamental physics of its operation. Called "state estimation," it takes a few minutes to develop a comprehensive picture of the grid that can be used also for contingency analysis to determine likely outcomes and potential next steps.
"By advancing the architecture and the algorithms and specifically tailoring them to the problem at hand, we've already sped up this process by an order of magnitude," Pratt said. Right now, researchers depend on high-performance computing capabilities of DOE's Office of Science for these breakthroughs, but Pratt said it won't be long before this kind of processing will become available in mainstream systems for utilities.
The EIO Initiative also is focused on research to help understand the dynamics of the electric grid and build those properties into improved real-time models. Today's operational models assume that the grid is in a steady state, ignoring oscillatory behavior that can potentially bring it down. Current studies of the grid's dynamic stability are so slow that they're typically done offline and can't be incorporated into control processes. Without precise models, the grid is often operated with more margin than needed, which results in real economic impact. The Initiative centerpiece is the Electricity Infrastructure Operations Center, a fully capable grid control center that serves as a platform for grid research and development, testing and training (see related story, next page).
As demand for electricity continues to grow, the existing transmission and distribution system will continue to get pushed to its limits, threatening its reliability. "We can't afford to goldplate the grid to make it reliable," Pratt said. "Instead, we're focused on how to safely live close to the edge—knowing with confidence where that edge really is—while keeping the lights on."