Considering Communications for AMI

By Bob Heile, IEEE’s 802.15 Working Group on Wireless Personal Area Networks, P2030 Work Group Task Force 3 and the ZigBee Alliance

Utilities’ and customers’ expectations from advanced metering infrastructure (AMI) vary widely among markets around the globe, and they will rapidly evolve in many directions as smart grid rollout intensifies and system and process innovations emerge. As a result, AMI communications needs are a moving target.

Utilities must take aim anyway.

“It’s critical to not think in terms of a short-term solution,” said Jim Cherrie, director of deployment for the Edison SmartConnect program at Southern California Edison, a utility that is investing $1.6 billion in grid technologies.

What factors must utilities consider in constructing secure AMI communications infrastructure? The challenge is to develop an approach that is cost-effective today and seamlessly compatible with tomorrow’s smart grid applications that enhance grid management, service reliability, distribution automation, operations efficiency, usage options and pricing flexibility.

User to AMI, AMI to Utility

Technologies and techniques that enable AMI communications can be viewed in two dimensions: AMI must collect the data from points of use within a facility and the utility then must extract the data from the meter.

Though one preferred primary solution may exist, it’s reasonable to assume that multiple solutions with roles in enabling home area networks (HANs) will be developed, allowing residents to more intelligently manage electric usage and take advantage of time-of-use pricing. The disparate HAN-connected devices might include smart thermostats and appliances that an individual could move from one side of the country to another. The scenario tees up communications interfaces requirements—universality, portability and mobility—across multi-vendor HAN devices and AMI solutions.

The communications challenge in the link from utility to AMI is a seamless, cost-effective interface with meters fixed on buildings. Full coverage and maximum reliability are key requirements. Communicating with 999,999 of 1 million customers is not good enough; a utility must be able to efficiently and reliably reach 100 percent of its base. In addition, polling rate and latency requirements must be considered.

These requirements illuminate the need for consensus standards in AMI communications.

“We definitely believe standards are going to be the key to success,” said Cherrie. “And utility participation in standards development is crucial because we are the ones who are experiencing things firsthand. We’re learning new things all of the time.”

IEEE 802.15.4g is being developed to serve the needs of the utility-to-meter communications link and ZigBee Smart Energy Profile based on IEEE 802.15.4, which is the leading standard for the meter to HAN.

Communications Choices

Beyond ensuring portability for devices communicating from home to meter and full coverage and maximum reliability of communications from meter to utility, the next hurdle in constructing an AMI communications infrastructure centers on understanding what applications must be sustained.

Some utilities around the globe appear to be deploying AMI primarily for operational efficiency (eliminating the need for manual reading of older, mechanical meters) and plan to link with customers via third-party Internet connections. Are these connections through customer-owned routers, which may or may not operate properly at a given moment, reliable enough for to support load-disconnect systems and time-of-use pricing? Utilities will depend on this information to handle customer repudiation. For example, AMI communications path integrity will become central to how utilities operate.

According to its website, Southern California Edison (SCE) has an ambitious goal of enabling its customers to monitor their electricity usage and costs through the Web as easily as they check their families’ mobile phone usage or bank balance. SCE plans to send signals to smart appliances connected through customer HANs about system demands at a given moment and customers will be able to program those appliances and devices to respond automatically and take advantage of flexible pricing models.

Southern California Edison began installing smart meters in 2009. Rollout of the Edison SmartConnect metering system continues community by community across the utility’s 50,000-square-mile service area. With more than one million meters already installed, Southern California Edison plans to have deployed about five million smart meters for residential and small-business customers by the end of 2012.

To enable communications around its AMI deployment, the utility constructed a multi-tiered infrastructure designed for efficient operations, robust traffic security and flexible tariffs and programs. It’s a cellular-based wide area network (WAN), with two-way narrowband 900 MHz radio frequency (RF) wireless communications to the meters and integrated ZigBee Smart Energy standards-based HAN communications at 2.4 GHz RF using IEEE 802.15.4.

“We sought a platform to accommodate our needs of today and tomorrow,” said Cherrie, who oversees product management, field deployment and the Edison SmartConnect Operations Center. “We sat down with a blank piece of paper and asked, “ËœWhat can take us to the next level? What does the utility of the future look like?’ And we spent more time in R&D than most utilities are maybe accustomed to.”

Bandwidth and Beyond

Forecasting smart grid bandwidth needs for the utility-to-meter network can be tricky, especially given that needs could evolve dramatically as innovation around rollout intensifies. As mentioned earlier, bandwidth, response times and latency requirements are among the basic performance parameters that utilities must consider, in addition to the basic communications needs of AMI. Utilities may also need a communications infrastructure capable of supporting remote testing, maintenance, monitoring and upgrade services from the utility to AMI. Even with those additional requirements, however, unless a utility plans to enter the Internet-communications business or offer data-intensive services, broadband is probably not necessary.

Utilities are communicating primarily with sensors and controllers (not much in the way of broadband) and will continue to do so. Even with AMI producing significantly more information at more frequent intervals than utilities have collected before, the number of bits per second is small when compared to applications like large file transfer or streaming audio or video. SCE residential customers can view their usage data hourly and business customers in 15-minute increments.

“You have to consider the role of the meter going forward.” Cherrie said. “For now, the speed, performance, security and remote upgradability of the meter and communications system is meeting all of our needs with room to spare. In addition, one of the key assumptions we built into our business case was that we would be reviewing our backhaul approach once every five to seven years.”

The smart grid is a learning process, Cherrie said. When SCE began planning its AMI system operations center, those involved asked what it would take to operate the system.

“Initially, we thought it would probably be like a traditional telecommunications NOC (network operations center),” Cherrie said. “We quickly realized that it’s nothing like a NOC. We’re not just looking at in-house systems; we’re looking at the convergence of technology, metrology, security, telecommunications and predictive modeling for five million intelligent devices in the field.”

Activities such as standards development provide an opportunity for utilities to share what they’ve learned. More than 100 utilities from around the world have turned to SCE for best practices on smart meters, synchrophasor measurement, electric-vehicle and renewables integration, energy storage and other smart grid technologies.

One lesson that utilities are learning as they introduce AMI is that the demand-responsive smart grid’s concept of two-way communications and control is largely uncharted territory for the power industry. It demands new technologies, processes and skill sets, as well as a set of consensus-based standards optimized to support it, which is the mission of groups like IEEE P2030, IEEE 802 and the ZigBee Alliance.

This article is the third in a series of articles on metering by Bob Heile. His first two articles in the series were in the July 2010 and August 2010 issues.

Bob Heile is a 30-year veteran in data communications and wireless data. He is the chairman and founding member of the IEEE 802.15 Working Group on WPANs, chairman of the ZigBee Alliance, co-chairman of IEEE P2030 Smart Grid Communications Task Force and is a founding member of 802.11. He holds a bachelor’s degree from Oberlin College and a master’s and doctorate in physics from The Johns Hopkins University.

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