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Grid Futures

Evolutionary directions for electric system architecture.

Fortnightly Magazine - April 2011

does become crucial for T&D operation is in supporting operators’ situational awareness, equipping them to maintain system reliability. Wide-area situational awareness would likely be the most acutely felt need for intelligence in the beefy grid.

As in each scenario, the form of the beefy T&D system can be expected to follow function. Transmission towers and lines will be a major visible presence, with new links traversing the countryside to connect distant resources with metropolitan areas. Numerous wind farms likely would crop up in the central United States and solar arrays in the Southwest, sited and scaled so as to make optimal use of resources. Because of the need to complement the short-term intermittency as well as the seasonal availability of different renewable generation resources, a high-voltage interstate highway would span the continent, with a capacity that represents a significant percentage of total demand in the eastern and western U.S., respectively. Probably the key aspect of the beefy system’s overall look, therefore, is that T&D facilities increasingly cover sparsely populated land areas not previously associated with much electricity infrastructure.

In the “nimble” scenario, the T&D system’s function can be more broadly described as connecting supply and demand of electricity, probably accommodating a broader spectrum of generation. Specifically, if technology implemented at the distribution level affords more refined voltage control and sophisticated protection coordination algorithms at reasonable cost, higher penetration levels of small- and medium-scale distributed generation become a viable option to complement central-station plants. The need for adding transmission hardware would be less pronounced, partly due to more distributed generation, and partly due to technical options such as routing intelligence ( i.e., power flow control) and increased utilization of existing lines. Because building out T&D capacity in the traditional way and improving asset utilization through technology are both feasible, the nimble scenario could be called “have-your-cake-and-eat-it-too,” with the motto “Deliver a kWh from anywhere to anyone, anytime.” The extent to which new technologies are integrated would depend on the details of local constraints and cost-benefit optimization.

Indeed, optimization would become the name of the game, as more than one viable solution would exist for relieving any given set of operational pressures. Rather than playing defense against encroaching constraints, T&D operators and planners could be proactive in comparing and choosing among solutions that afford desired gains. Overall, therefore, the “nimble” scenario would offer flexibility, adaptability and resilience. Operationally, the biggest challenge of the nimble scenario could become processing a large volume of information from different levels and sources into effective operating actions, spanning many orders of magnitude on both time and distance scales. 6 Some important questions would include how information is aggregated and which processes can and should be operated in closed-loop automation mode. The benefit of an extended menu of hardware and intelligence would also entail challenges at the planning and design level, since the analytic tools (not to mention criteria) for optimizing system function with so many diverse variables have yet to be developed.

It seems safe to say, nevertheless, that the T&D system’s relative trend from Quadrant I toward