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The smart grid is bringing the electric utility industry into the 21st century. In combination with smart meters, the smart grid enables consumers to monitor their energy usage. For utilities, it eliminates house-to-house meter reading, makes possible the remote connection and disconnection of electric power, and sends automatic alerts when outages occur.

The smart grid enables retail electric providers to offer time-of-use rates that differentiate peak and off-peak consumption to encourage electricity consumers to shift their consumption patterns accordingly. It also enables consumers to support the integration of distributed generation (for example, electric cars, wind turbines and solar panels).

But the smart grid is only as smart as the communications network that ensures the rapid and reliable two-way transmission of all this data. Over the past three years, CenterPoint Energy (Houston, Texas, U.S.) has been installing just this kind of advanced communications network.

Network Requirements

The mass of information accumulated by smart meters is of no value unless it can be transmitted reliably to the utility data center and processed. Hence, there is a critical need for an effective communications network.

To create such a network, CenterPoint worked with IBM, Itron, GE and Quanta Services. Each of these vendors has made a contribution to the network's success:

IBM's network methodology was the basis for the network's architecture.
Itron provided meter, cell relay and system hardware, software and services.
GE provided WiMAX radios/antennas, management software and services.
Quanta provided meter and communications equipment installation services.

CenterPoint had seven exacting requirements for its communications network:

Have a comprehensive coverage design for a 5,000-sq-mile (12,950-sq-km) service area.
Provide two-way communications to endpoints (that is, to cell relays [meter data collectors] and intelligent grid switching devices).
Have data throughput capacity sufficient to transmit 96 interval readings a day from each of more than 2 million meters, and to execute all service orders generated.
Be reliable in all conditions, particularly storm conditions as the Houston area is susceptible to hurricanes.
Be secure, adhering to strict cyber-security standards.
Be scalable to keep pace with ever-increasing amounts of data as more smart meters and intelligent grid switching devices are installed in the years ahead.
Have adequate fail-over and redundancy to ensure backup in the event of a component failure.

Architecture Development

IBM's network methodology was used to help CenterPoint develop the communications architecture for the smart grid. This methodology is represented by a collection of development templates, best practices and procedures for designing networks. The development process is structured in phases, from the requirements, to conceptual modeling, to logical modeling and, ultimately, to the final detailed network design.

The end result of this development process was a communications network design in which the meters form a mesh and communicate through cell relays. The design ratio of meters to cell relays is roughly 400:1. In the event a cell relay fails, the meters associated with the failed cell relay will migrate to an adjacent cell relay.

From the cell relay, there is dual-path (primary and secondary) communications architecture. The primary communications path is the company's private WiMAX network, consisting of radio towers, typically at substations, which connect to nearby cell relay sites. A failure of any segment of the company's WiMAX backhaul communications will cause the cell relays associated with that segment to fail over to the secondary path, a public cellular carrier (AT&T) network.

The smart grid communications model was developed as an end-to-end design with dual communications paths to provide redundancy. By implementing a private wireless infrastructure as a primary communications path and using a public cellular carrier as the secondary path, CenterPoint was able to use the full strengths of both types of networks to create a reliable solution. This redundancy and resiliency enables CenterPoint to live up to its brand promise: “Always there.”

Communications Network Build

Smart meters transmit electric usage data wirelessly to cell relays installed on electric distribution poles connected to both the WiMAX and cellular networks. More than 5,200 cell relay sites have been built across Houston to communicate with the more than 2 million meters installed across CenterPoint's electric distribution territory.

The cell relay location consists of a cell relay, a wireless WiMAX remote radio and an antenna — all of which are powered by electricity from the power line with battery back-up. For approximately every 75 cell relay locations, there is a WiMAX radio tower site that functions as a take-out point (TOP) to collect the data.

At the cell relay sites, communications crews program the WiMAX radio and then align the antenna to ensure the radio is communicating with the TOP. TOPs, which are built mainly at CenterPoint substations, collect data from cell relays within a several-mile radius and deliver the data, through the microwave and fiber backhaul network, to the data center.

The TOP consists of a 150-ft (46-m) steel lattice tower or pole. On the structure, crews installed three WiMAX antennas, spaced 120 degrees apart, to receive signals from surrounding cell relays. In addition, crews installed and aligned the microwave dish to connect with the core network through an adjacent microwave location. The telecommunications equipment for the TOP is sheltered inside a concrete building at the base of the tower or pole. Cell relay data collected through one of three master radios — one for each antenna — is routed over the microwave network by fiber-optic cable to the data center.

A data collection engine passes information collected from the cell relays to the meter data management system, which processes and stores meter data and also executes service orders. CenterPoint sends meter data to the Smart Meter Texas web portal, where consumers may securely view their historical 15-minute usage data in 24-hour, 30-day and 13-month snapshots.

The Network Takes Shape

More than 2.2 million smart meters have been deployed, along with 5,220 cell relays and 140 TOPs. With these in place, more than 2 billion intervals of usage data are being recorded and made available to consumers on the Internet each week.

In 2012, CenterPoint has obtained 15-minute interval data at a rate of 99.3%, along with 99.8% of monthly register reads used for billing. More than 97% of service orders have been completed electronically, typically within 30 minutes, saving nearly 3 million truck rolls, with concomitant savings in fuel and reduction of carbon emissions.

Considerations and Lessons Learned

The real test of a communications network is how it functions in practice. The deployment process posed its own challenges and taught some significant lessons:

Communications network development must be closely coordinated with the meter deployment. CenterPoint's meters were deployed by route, and the network communications infrastructure was in place and stable three months ahead of the meter deployment. This approach allowed meters to begin communicating with the system immediately.
Be prepared to use creative design and installation solutions to meet aggressive time lines. For example, one of the tests performed at potential cell relay sites was to determine WiMAX signal strength to the WiMAX take-out site. When signal testing to a cell relay site was needed before the take-out site towers were built, large cranes were used to position the antennas at the appropriate height.
Complete the design of the overall communications system up front. Integrate all communications components into an overall architecture, test and analyze all equipment, complete construction standards, identify all construction materials and validate installation procedures through testing and training.
Manage materials and multiple service suppliers closely and establish strong field coordination along with detailed construction and performance acceptance and testing processes. Major equipment and long-lead items such as cell relays, radios, network electronics, towers and buildings need to be specified, bid on and ordered well in advance, and inventory levels maintained in a warehouse system and tracked. Given the fast pace of deployment, inadequate inventory can cause significant schedule disruptions.
Be prepared to support the infrastructure operationally when the first device goes into production. Identify staffing requirements and analyze, select and implement network management tools as they are used both for construction and for connectivity testing and operations.
Leverage a common communications infrastructure. The intelligent grid network is built to leverage the advanced metering system communications infrastructure so remote or automated switching commands are executed over the same network from which electric usage data is communicated.

Keys to Deployment Success

An effective communications network has CenterPoint positioned for the future. The smart grid is not only the future for CenterPoint, it is the future of the utility industry. With this in mind, the following approaches may be considered when planning any smart grid communications system:

Establish a strong governance process. A strong project management office, using a proven governance methodology, is essential to the overall success. With the deployment of any integrated system, especially one as complex as an advanced meter system, the application of consistent scheduling, financial, scope, change and reporting processes is imperative.
All project teams and support functions should be integrated and closely aligned within a project management structure overseen by a robust project management office.
Develop solid business and technical requirements and ensure agreements with all stakeholders.
- Apply a proven network architecture development method to ensure a solid design that meets requirements.
- Ensure the deployment of smart meters and switching devices is coordinated closely with the deployment of communications infrastructure.
- Adopt and follow efficient, safe and cost-efficient design and installation standards, keeping in mind operational support requirements.
- Minimize exceptions; they add costs and delay progress. When unavoidable exceptions do occur, handle them aside from the main deployment effort in order to avoid disrupting the primary deployment routine.
- Follow up the deployment as soon as possible with a plan to operate and maintain the equipment and systems.

The smart grid is becoming the norm in the United States, and the nerve center of every smart grid is the communications network that connects it. CenterPoint Energy's experience will not be the exact experience of every utility as it moves to the smart grid. But the lessons learned during this process may prove useful to other utilities that are on the various steps of this path.

Chuck Hackney ([email protected]) is the director of Telecommunication Services & Smart Grid Communications. He manages the CenterPoint Energy backhaul and smart grid network and is responsible for the smart grid communications network deployment. Hackney has deployed large technology infrastructures, re-engineered business processes and developed organizations for both large technology infrastructure deployments and the resulting operations. He has held management positions in T&D, power engineering, SAP project, IT and operations technology organizations. He holds a BSCE degree and is a licensed professional engineer in the state of Texas.