Friday, November 13, 2009

Set Phasors to Smart!

While Google was making a splash in early October opening up its API for web tool PowerMeter, the Tennessee Valley Authority (TVA) was quietly stirring up its own waves by making its SuperPDC available to others in the power industry. The SuperPDC, a phasor data concentrator, is a computer system used to determine the health of the power grid. Whereas Google's PowerMeter monitors home energy use, the SuperPDC collects and monitors information on the entire eastern U.S. power grid. Despite the difference in scale, both recent announcements indicate steps being taken toward the creation of the smart grid.

Time seems to be moving faster than what anybody imagined. In the Jan/Feb issue of Electric Energy T&D Magazine, the article, “Phasor Measurement Units - From Exotic to Everyday,” explains how the authors implemented a simple approach to PMU (phasor measurement unit) technology over the past three years at the Salt River Project in Phoenix, Ariz. At the end of the article, authors Gary Roskos and Bill Robertson are predicting that the more widespread use of PMUs would “lead to advances in distributed real-time dynamic stability control applications.” Translating engineer-speak, that means applications like the SuperPDC which “would lead to the development of control algorithms… to preserve the integrity of the overall Grid.”

The SuperPDC collects its information from PMUs which are often situated at critical points in the grid such as generation sites and control area boundaries between a utility and its neighbors. The Electric Energy authors recommend asking three questions when locating PMUs: 1) What data is needed by regional organizations and neighbors?, 2) Where is system observability poor or estimation/measurement errors are high?, and 3) Where are elements, such as transformers or phase shifters, where impedance models vary?

PMUs will be the sensor workhorses of the smart grid by measuring electric current 30 times per second, with each measurement carrying a time stamp taken from GPS (Global Positioning System) satellites. By being able to monitor and report line conditions in real time, PMUs and PDCs enable more power to flow over existing lines. And, the system of sensors and software are integral to meeting the Department of Energy’s (DOE) requirements for a smart grid -- one that is capable of sensing system overloads, preventing or minimizing outages and automatically “healing” itself when variances occur in the power grid.

As the nation’s largest public power provider, TVA has always been on the vangarde of development. The success of the SuperPDC has led the North American Electric Reliability Corporation to contract with TVA to expand the system into a regional PDC. Wide industry use is targeted for the beginning of 2010. The use of phasors and the software systems that record and analyze their data are one of the most important steps in the improvement of the nation’s power system for smart grid technology.

“We’re hopeful that TV’s technology will enable both computer system vendors and the electric power industry, as billions of dollars are invested, to modernize the power grid over the next several years,” said Jacinda Woodward, TVA Vice President of Power Control Systems.

TVA announced its open PDC approach at a meeting in Chattanooga, Tenn., led by the North American Electric Reliability Corporation. Utility representatives, computer system vendors and power grid researchers attended. Such meetings, of course, can only help to advance the clock as interested parties around the country conduct their own experiments in setting the grid to smart.

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