The operations and planning rules for integrating variable resources aren’t the same across the electric power industry in the United States at present. Opinions are somewhat divided about what...
Demonstrating the Smart Grid
Pilot projects clarify the vision of an intelligent utility system.
from several seconds to 10 minutes were observed. What was typically a momentary interruption went unnoticed by the consumer, but the study found that controllers have the technical capacity to act as a shock absorber for the grid and prevent or reduce the impact of power outages.
Addition Through Subtraction
The GFA results are interesting from a number of perspectives. For example, the controller works autonomously, so all that’s needed is a wall outlet. Because its under-frequency threshold is higher than the threshold at a substation, the controller theoretically could reduce the chance of a feeder blackout by anticipating and responding to an under-frequency situation first, before it reaches and triggers the substation relays.
The protection results in little or no inconvenience for the appliance owner, while a substation relay action creates outages for many customers on the downstream feeder, and such an arrangement certainly would be preferable to having designated commercial and industrial loads curtailed at the utility’s expense.
“In a sense, you’re buying electricity from a demand-response network, not a peaking reserve unit,” Pratt says. “This could reduce the need for load following power to regulate the frequency of the grid, which fluctuates daily. Why burn a lot of fuel to follow that load during what is usually a 10 to 60 second event?”
Finally, such an arrangement could make it easier for utilities to rely on renewable energy sources like wind and solar farms. As an example, Pratt points to a February drop in frequency on Texas’s transmission grid related to a shortfall in output from the state’s wind projects.
“They couldn’t bring up their spinning reserve fast enough,” Pratt says. “They had a sledgehammer approach in that they had to interrupt targeted customers. Whether it’s a price dispatch approach, or a circuit board built into a home appliance, we’re proposing to do the same thing, but with finesse.”
An Intelligent Switch
A major utility in the Midwest has been experimenting with smart-grid technologies since the mid-1990s, and today it uses those technologies to get the most out of its old-tech infrastructure. (Editor’s note: As this issue was going to press, the utility’s lawyers intervened and requested we not name the company in this story because of pending litigation and ratemaking issues. As the company’s spokesman explained, they’re facing disputes over such basic things as the definition of “smart grid,” and whether the company’s grid already is smart enough to do what’s necessary to serve its customers.) The company uses Cellnet+Hunt UtiliNet communications devices to help monitor and operate the 34-kV sub-transmission system that feeds its distribution substations.
A web of roughly 3,500 Cellnet wireless devices are programmed to carry out a variety of functions and transmit real-time operations data back to the utility’s SCADA system. Each device sends its signals via a mesh network of Cellnet transmitters strategically located throughout the utility’s service territory.
The utility has 900 automated switches on the 34-kV system, and each has the ability to reconfigure itself to restore service during an outage, and report its actions back to its SCADA system. If,