11.19.09Stephen Hadden, Senior Consultant, R.W. Beck, an SAIC Company

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This is the fourth in a series of articles on practical Smart Grid approaches that utilities can initiate now.

When Will Smart Grid Be Available?

The concept of an intelligent electric utility infrastructure or "Smart Grid" is attracting wide interest among utilities, consultants, regulators and other utility stakeholders. This interest, however, is accompanied by widely differing expectations about when Smart Grid will emerge. Some confidently proclaim that the Smart Grid is here or just around the corner. But utility management and staff responsible for operating real electric systems are understandably cautious. They realize that Smart Grid will not suddenly become available in a suite of closely bundled technologies and applications. And they are pragmatic about the technology needed today to improve distribution operations for the next few years.

We Can Make the Grid Smarter Right Now

The concept of intelligent infrastructure will continue to evolve, but utilities have practical choices now. They do not have to wait passively to provide effective solutions as Smart Grid develops. Utilities can begin using existing and emerging technologies and applications to create something we call an "Agile Grid," on the way to creating a Smart Grid. Many utilities already have deployed, or are planning, key elements or components of an Agile Grid.

While there are numerous examples of these technologies and applications, in this article we discuss just one: using the advanced metering infrastructure (AMI) communication network for distribution automation (DA), which is a major function of Smart Grid. Until the emergence of AMI, DA was basically an extension of SCADA beyond the substation gates. Using SCADA as a platform for DA away from the substation is still an option for many utilities, but DA that leverages SCADA is generally limited to substations because the SCADA communication infrastructure does not readily reach out along feeders into the distribution system.

Many utilities are interfacing their AMI with other automation resources to exchange data and develop actionable information, which is needed by utility staff to improve reliability, efficiency and operations. This view of the Agile Grid concept is illustrated in the diagram below. The interface between AMI and DA is shown by the dark arrow. Utilities can use their two-way AMI to enable an Agile Grid by using the AMI communication infrastructure to support basic DA functionality, such as monitoring and remote operation of distribution line reclosers, motor-operated switches, capacitor banks, voltage regulators, etc. Traditional SCADA can provide better bandwidth and latency than most AMI, but the AMI communication infrastructure extends to all meters and, typically, to all distribution line devices. Also, AMI bandwidth and latency are generally adequate for these types of distribution applications.

AMI Improves Agility of DA

In an earlier article in this series on the Agile Grid, we described how AMI outage notification can improve performance of utilities' outage management systems. Features and capabilities to support DA applications vary by AMI vendor, but the AMI communication infrastructure can be used by utility staff to improve outage restoration and reliability. For example, switches may be operated remotely to transfer load and restore service to some customers while isolating trouble to the affected line segment. Also, after line repairs are completed, utility staff can use the AMI communication infrastructure to remotely close the tripped recloser and return all switches and loads back to their normal configurations. While this is not a realization of the future "self-healing" concept of Smart Grid, utility staff can use the AMI communication infrastructure now to enable a more Agile Grid that effectively leverages the utility's present resources to improve reliability.

Also, in another Agile Grid article, we described how AMI load data may be used by utility engineers to use engineering analysis as a planning and operational tool. We described how AMI load data enables utility engineers to perform near real-time distribution simulations and analyses. One byproduct of these studies is the preparation of contingency switching analyses that can be implemented using the AMI communication infrastructure, as previously discussed. Also, this DA switching capability may be used by utility staff to switch loads to alleviate thermal loading and improve voltage levels. Alternately, AMI is an enabling technology for direct load control and other demand response programs that reduce peak loads on distribution facilities.

In the next Agile Grid article, we will expand the discussion of direct load control and demand response, and describe how AMI can be used to implement conservation voltage regulation.

Agile Grid Today -- Smart Grid Tomorrow

Widespread automation throughout a typical distribution system may someday be available and affordable. Information about critical distribution functions is one of many Smart Grid deliverables envisioned. A utility's two-way AMI can prioritize data traffic within the communication network to ensure that important DA alarms and other information are quickly presented to utility staff. Although this capability did not exist just a few years ago and it may not be considered Smart Grid by some, it is part of an Agile Grid that is readily available to utilities today.

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