Southern California Edison envisions an advanced metering system that brings customer-usage data into the digital “central nervous system” of its power operations. This information backbone would enable dynamic pricing, demand response, efficient customer management, and rapid outage and theft detection. Customers would see and could react to their energy usage on a daily basis. It also would provide the utility with tools to react to emergency situations. Eventually, it could permit real-time feedback between customers and energy markets, and enable customer-owned distributed generation. This would streamline utility operations and reduce day-to-day operational costs.

Recently, SCE (Rosemead, California, U.S.) developed the functional requirements and specifications of a new advanced metering infrastructure (AMI) project. Although the pilot test is still in development, if the system is cost-effective and approved by the California Public Utilities Commission (CPUC), SCE will start deployment in 2008. The system envisioned will replace about 5 million meters and will cost approximately US$1.3 billion in capital funds with full deployment in 2012.

The AMI project will leverage commercially available components using open designs for both metering and communications, creating a flexible and sustainable technology platform. Open design facilitates the use of both existing and future technology developments in home connectivity, distribution grid intelligence and distributed generation. Keeping upgradeability in mind, the millions of meters in an AMI must be adaptable to new technologies, programs, rates, applications and security threats. Furthermore, the AMI must be technically and economically feasible for SCE to perform these upgrades at minimal costs.

The approach to achieve this openness and upgradeability follows a modern systems engineering approach for evaluating the benefits and risks inherent in deploying such a complex system. The increasing pace of innovation within AMI technologies presents opportunities and challenges. Equally important is the ability to balance cost, schedule and technical constraints with a thorough understanding of the maturity level of available technologies. SCE's systems engineering approach provides a structured framework for addressing these issues.

With the goal of an open design, SCE leveraged the results of prior open-architecture efforts, including EPRI's IntelliGrid Architecture project, the OpenAMI Task Force and the Interoperability Constitution of the U.S. Department of Energy's GridWise Architecture Council. These provided the initial framework and scope for the SCE requirements gathering process.

An important decision was adopting “use cases” to gather AMI system requirements. Use cases have become a proven method for collection and documentation of system requirements in the software industry (see the table). Both the IntelliGrid and OpenAMI projects were based on use cases, and IntelliGrid had provided a methodology developing them. SCE's use cases and requirements have been released so that other utilities, standards bodies and industry groups can benefit from the lessons learned.

To apply this approach, SCE engaged EnerNex Corp. and IBM as consulting system engineers responsible for assisting in use-case development, requirements capture, analysis and system architecture design. IBM brought its extensive expertise in large systems architecture development and integration. EnerNex, which has been a member of the EPRI IntelliGrid Architecture team since its inception, also developed the California Energy Commission's reference design for demand responsive infrastructure and was responsible for the formation of OpenAMI. EnerNex was in a good position to transfer those lessons learned to this AMI project.

To develop requirements based on use cases, SCE organized a series of workshops using cross-functional teams. Use cases place particular emphasis on how the metering system will actually be used rather than being constrained with existing product designs. The intent is to clearly define the desired requirements, leaving vendors free to provide innovative solutions. The requirements teams analyzed 18 separate use cases in 6 categories, representing 99 separate potential scenarios of how AMI might be used to improve service levels, lower the costs or both.

With the use cases finalized, the requirements were consolidated resolving any conflicts and ensuring consistency of terminology and language across all the requirements. The resulting consolidated requirement set was then prioritized and mapped to architectural components and functional areas. SCE's preliminary requirements for AMI was published on June 30, 2006.

SCE's systems engineering approach is use-case driven and focused on identifying the architecture components necessary to enable the system requirements. By mapping each requirement to a technology neutral or generic component, a set of required capabilities is described for each component and subcomponent. This yields a conceptual architecture view of the entire system describing how components will work together to deliver the value captured in the business case.

This process results in a series of engineering decisions that yield a platform-independent, preferred system design. SCE's preferred system design, represented in the conceptual architecture, serves as input into vendor evaluations, business-case estimates, integration and testing plans. It also provides a means to accelerate platform-specific AMI engineering and deployment tasks once a specific set of technologies has been selected.

The challenge in communicating the conceptual architecture for AMI lies in the complex collection of devices, data, networks, computer systems, protocols, organizational processes and people necessary to provide the operational benefits. To address this challenge, it is helpful to think of AMI as a “system of systems” working together to provide value to a common set of stakeholders.

SCE's systems engineering approach yields views of the AMI architecture at increasingly lower levels of abstraction by answering the following questions and describing the answers in a system of systems context.

• Why? Requirements definition, the first step in the design process, answers the question, “Why are we investing in this project?” As the cross-functional teams developed the AMI functional and nonfunctional requirements through the use-case workshops, they identified the business value of each requirement. Business-case teams then investigated in detail to assign a dollar figure to each identified value statement. The result became SCE's conceptual business case for AMI.

• What? Conceptual architecture answers the question, “What systems, subsystems and components do we need in order to meet SCE's requirements?” To provide these answers, the system architects translated the steps of each use case into a matrix of abstract message sequences passed between a set of “actors.” Eliminating duplicate messages and actors produced a well-defined set of logical interfaces and components.

• How? Logical reference architecture determines how the AMI components are integrated into a logical architecture and what services must be provided to create a viable end-to-end solution to fulfill the goals. This view of the AMI architecture also provides a refined answer to the question, “How much value (costs versus benefits) does each alternative architecture and component yield, and what are their constraints and boundaries?”

• With what? Platform-specific reference architecture determines: “With what standards, technologies and vendor solutions will SCE select to accomplish our AMI goals?” The outcome of this process is the selection of specific vendor solutions necessary to meet the requirements required to achieve a positive operational benefit. This is the lowest level of design abstraction prior to commencing detailed design and integration activities.

The success of the SCE AMI project has a great deal to do with three key principles on which the process was based:

• Firstly, SCE has found that applying a disciplined systems engineering approach to developing its AMI has resulted in an architecture that is extensible and capable of being implemented using available technologies. This approach has produced requirements that reflect the needs of a wide base of stakeholders from both inside and outside SCE. The methodology allowed continuous involvement of the vendor community to ensure that they understood the requirements and provided valuable feedback to SCE to validate that implementation was feasible.

• Secondly, nearly as important as the use of top-down systems design was the early commitment to an open architecture and transparent engagement with the rest of the power industry. Using the IntelliGrid architecture, GridWise principles and work products of other organizations such as OpenAMI provided a strong foundation and architecture upon which the SCE AMI system is based.

  To show its commitment to open innovation, SCE has made its work products available to the industry through a variety of venues. SCE has published its regulatory filings, use cases, requirements, technology capability methodology, presentations from vendor and external advisory group meetings, and other documents on its website (www.SCE.com/ami) throughout the project and will continue to do so. SCE also has contracted with EPRI to merge the final use cases and requirements back into the overall IntelliGrid architectural model.