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Data Transport for First-Generation Smart Grid

Aug. 22, 2013
A telecom and electric utility partner to deliver wireless broadband throughout Vermont and ubiquitous backhaul services.

A Vermont utility and a Vermont telecommunications company are partnering to leverage a new fourth-generation long-term evolution (4G LTE) network that will deliver wireless broadband services throughout Vermont and meet the needs of utility smart grid applications for ubiquitous, service-level-based backhaul services.

Green Mountain Power (GMP) is an investor-owned utility serving about 72% of all electric customers in Vermont, a rural state with bucolic hills, beautiful farms in the valleys, charming small towns and a tourist industry that benefits year-round from a variety of seasonal sports and outdoor activities. The winters are cold and snowy, and the Green Mountains and Taconic Mountains bisect the state north to south. With about 625,000 residents and 330,000 electric revenue meters, the state is lightly populated.

These same dynamics, which make Vermont an attractive place to live and vacation, make it a difficult place to develop telecommunications infrastructure. Vermont’s regulatory structure includes a quasi-judicial body called the Public Service Board (PSB) as well as a Department of Public Service (DPS) that represents the public interest and reports to the governor.

A Statewide Collaboration

GMP’s smart grid program began in early 2008 with close collaboration among Vermont utilities, regulators, customers and other stakeholders to develop a shared understanding of smart grid facts and benefits. This collaboration took the form of a docket opened by the PSB. Initially, a series of workshops defined smart grid, developed a shared understanding of the technologies, identified quantifiable benefits, established minimum requirements and optional characteristics, and defined ground rules for rate recovery.

Ultimately, this collaborative group successfully secured a US$69 million federal smart grid investment grant supporting $138 million in projects to implement smart grid infrastructure and programs throughout the state.

This voltage sensor for volt/VAR optimization uses a CalAmp Fusion modem (box on the right) for backhaul communications. Two antennae are mounted above the gatekeeper box. The disconnect switch above them allows a tech to cut power for service.

The Backhaul Dilemma

Smart grid requires that commands and data flow easily among smart devices throughout the electric system. The communications backbone that carries this flow is commonly called backhaul. The federal grant made the deployment of smart grid technologies a foregone conclusion for much of Vermont. But the utilities and policymakers faced another challenge with no clear solution: What communications path(s) could provide the backhaul for the smart grid? Even in the most optimistic models, cellular data networks covered less than 70% of the state’s geography, and wired broadband alternatives did not fill the gap.

The population density (left) and topology (right) are the keys to the statewide communications development. The terrain/population challenges were the main drivers in having to find a new answer for backhaul in the first place.

In 2007, then-governor of Vermont Jim Douglas had declared the audacious goal of making broadband and cellular service available to all Vermonters by 2012. But in 2008, there still was no clear way to achieve this goal. History shows that, left to its own devices, a utility will build infrastructure owned and controlled directly by the utility in the interest of its operations, customer service and other priorities. The initial plan to achieve smart grid backhaul in Vermont was consistent with this tradition.

The initial plan called for enhancing the utility’s existing microwave networks, leveraging a privately licensed spectrum to achieve homogenous, secure, high-availability backhaul. This would have been a network of which any engineer would have been proud. It also was completely inconsistent with the policy framework that was developing in Vermont.

When the collaborative discussion on smart grid focused on backhaul communications for utility field devices, the paucity of telecommunications options was recognized as a big challenge. At the same time, it was clear the governor’s office and the DPS would not support utility investment in telecommunications infrastructure that did not support the state’s broadband and cellular goals.

In a memorable moment of the smart grid collaboration, the commissioner of the DPS banged on the table and insisted, “… every dollar spent on the smart grid must be leveraged to the greatest benefit of Vermonters!”

From this perspective, it was only natural to see the utilities and their now-funded smart grid projects as an opportunity to kill two birds with one stone for the state. The utilities were going to have to build communications infrastructure to enable a smart grid. So, why not build it in ways that also advanced public broadband access?

Collaborating Makes Sense

Because the utilities were collaborating on advanced metering infrastructure (AMI) procurement, it made a great deal of sense for GMP to find a backhaul solution that would meet both AMI and grid automation needs while also considering statewide policy interests. To satisfy these diverse interests, GMP looked at a wide variety of approaches that included private microwave, an integrated WiMax AMI solution and a cell-based AMI solution that possibly could have improved the public cellular network in the state.

Ultimately, GMP’s goal was to deploy AMI that would give customers the greatest possible value. Of all the options considered, the utility found that a 900-MHz radio mesh network would be the most cost-effective approach. For its combination of capabilities, cost and applicability to the state’s specific circumstances, GMP selected Elster’s EnergyAxis AMI.

Through the mesh network, meters relay messages to each other to reach a “neighborhood” node called a gatekeeper. Gatekeepers aggregate meter information and relay it to the utility data center. Backhaul to the gatekeepers can be through cellular modems, Ethernet ports and telephone landlines. Landlines are limited in their capability and stability and are a suboptimal backhaul method. The smart grid applications in GMP’s strategy depend on real-time communication with the gatekeeper. This requirement sets the standard for adequate backhaul and makes landline telephones acceptable only temporarily.

The VTel locations compared to the gatekeeper locations is a helpful illustration of the magnitude of the network and the relationship between LTE communications and AMI needs.

Next-Generation Wireless Emergence

A new option emerged with the potential to satisfy both the utility’s and public-policy needs. Vermont telephone and Internet service provider VTel previously had acquired Federal Communications Commission spectrum licenses in a combination of bands that covered the entire Vermont footprint. Perhaps VTel would partner with the utilities to apply a portion of that spectrum to meet utility network needs, allowing the utility investment to create seed infrastructure that VTel could then expand to support statewide broadband service for the public.

VTel management was hesitant in early discussions. They understandably viewed the spectrum as presenting a broad range of commercial opportunities that would be inconsistent with the idea of ceding a portion of the spectrum to utility applications. Ultimately, they decided that a full-fledged commercial LTE network would provide the best technical solution for a ubiquitous broadband network for Vermonters and represented the best opportunity for a sustainable business model for VTel.

As luck would have it, the U.S. Department of Agriculture’s Rural Utility Service (RUS) announced a grant opportunity in July 2009 specifically to improve broadband and cellular coverage for unserved and underserved communities. VTel was in an excellent position to submit a proposal tailored to the goals of the RUS American Recovery and Reinvestment Act grant. Since GMP had already been in conversations with VTel about a smart grid network, VTel was able to add backhaul for smart grid as an additional benefit of its project.

In August 2009, VTel was awarded a grant for the development of a LTE network to serve the communities targeted by RUS. Thus, the opportunity arose for GMP to alter its smart grid plans and embrace a brand-new commercially provisioned and supported LTE network for AMI backhaul.

Practical Considerations

While equipment was commercially available to VTel to develop the network and for consumers to attach to it to meet their broadband needs, no hardened customer premises equipment (CPE [In this context, the utility is the customer of the telecom company, so the utility’s communication boxes are CPE.]) was available. For the smart grid application, the customer premise for the network end points is in weatherproof boxes on utility poles. But at that time, all available CPE was for indoor environments only. A smart grid would require operation in the full range of New England weather.

Another challenge was that the schedule for the VTel network was out of sync with the smart grid implementation. In fact, the VTel network would still be in the engineering phase well into the rollout of meters and grid automation infrastructure. VTel’s network would not be in place when the AMI and grid automation needed a working backhaul connection.

This coverage map illustrates the portion of the VTel LTE network that was RUS funded. The GMP contributions helped fill much of the uncovered land within its service territory.

Regulatory Support

GMP had a splendid opportunity, but staying on schedule with AMI would necessitate interim backhaul solutions incurring short-term capital investments and operating costs until the VTel backhaul was available. The VTel project was in its conceptual stage, so production schedules were rough, at best.

Recognizing these challenges, costs and opportunities, regulatory support would be required to move forward. The now long-standing collaborative relationship with state authorities enabled the utilities to air these issues openly and reach a shared understanding. In January 2010, the regulators and utilities agreed it was in the public’s interest for the utility to work with VTel on smart grid backhaul.

Rolling Out the Network

Concurrently, the state’s transmission utility was installing fiber along transmission and subtransmission rights-of-way, connecting all substations. This provided a strong starting point for grid automation and created excellent communication to a significant subset of the AMI gatekeepers. The AMI network design started by placing gatekeepers at all substations.

To accommodate the misalignment of project schedules, practical backhaul solutions were required for the 75% of gatekeepers located outside of substations. GMP moved forward with AMI by leveraging a combination of communications methods so meter deployment could proceed.

This is a high-level illustration of the backhaul network and utility interfaces.

Workable backhaul options included cellular, digital subscriber line (DSL) and telephone lines. Cellular was the preferred method, because it allowed the greatest flexibility to relocate the gatekeeper as needed. It also had security advantages. However, cellular coverage reached only a portion of the remaining gatekeepers. To reach the rest, GMP used DSL, where available, reserving phone lines as a last resort.

As GMP rolled out the cellular gatekeepers, it found cellular service often was intermittent. The modems in Elster’s standard configuration gatekeepers were limited to 2G service. Replacing them with the CalAmp Fusion modems allowed the gatekeeper to use 3G, which expanded the coverage area and improved the stability of the cell-based communications network. This transition had the added benefit of pre-deploying the CalAmp LTE capability in the gatekeepers.

With the CalAmp modems in place, cutting over to the new VTel network would be a relatively simple matter of installing LTE sim cards, thus facilitating the transition to the new network as LTE sites were commissioned.

A Service-Level-Based Approach

By mid-2010, GMP and VTel had negotiated an agreement by which the utility would contribute to the VTel project and pay a nominal annual maintenance fee. The VTel network would be designed to accommodate the utility’s rigorous requirements for a variety of smart grid applications. These included service level, configuration, change management and coverage commitments that would meet and exceed the anticipated utility needs by a generous margin.

The VTel network capacity is allocated to GMP with no limitation on the number of devices GMP can deploy on the network. The agreement specifies a bits-per-month cap for GMP’s aggregate usage across the whole network. The cap provides ample room for growth over the course of the agreement.

The LTE network is engineered to serve required gatekeeper locations. The agreement ensures coverage for nearly all gatekeepers, with the stipulation that they may have to move up to 800 ft (244 m) in any direction. In practice, GMP believes it will be able to cover all gatekeepers. LTE installations included extended battery backup.

The LTE network supports quality of service class identifiers (QCI) settings that allow traffic from different sources and applications to be differentiated by priority. The VTel agreement assigns high priority for GMP traffic that has time sensitivity and criticality, while other traffic is set at a level consistent with commodity traffic. Service levels are monitored and QCI adjustments can be made to ensure compliance.

GMP traffic is segmented onto a virtual private network that separates utility messages from other network traffic. This facilitates tracking usage and message priority, and provides a mechanism for treating utility traffic with policy-based security in conformance with utility industry standards.

Current Status

As of this writing, the AMI network and virtually all of the smart meters are deployed. Back-office systems are processing a combination of interval and register data from meters. The fiber-optic network communicating with all substations is complete, grid automation infrastructure is operating in the substation, and pilot infrastructure is installed on distribution lines. The CalAmp modems have been fully tested on the LTE network and are widely deployed in gatekeepers, mostly operating on 3G cellular.

The LTE network is actively being rolled out, and GMP is transitioning gatekeepers to it as new radio sites are commissioned. Most importantly, GMP customers now have access to 15-minute interval data so they can better understand their electrical usage, and GMP is leveraging the capabilities of two-way communication with meters and grid control as well as monitoring devices to improve the services it provides.

The agreement between VTel and GMP establishes a model for collaboration between utilities and telecommunications service providers. This model can offer a potential win-win opportunity for other utilities, possibly with telecommunications companies, but also with other spectrum holders. One such opportunity might be recent rule changes that allow public safety entities to leverage their allocated 700-MHz D-Block spectrum in collaboration with utilities.

The circumstances that made this agreement feasible in Vermont were a combination of open-minded utility leadership, a willing and forward-looking telecommunications company, engaged policymakers and regulators, and capital available to support these innovative ideas. Ultimately, though, the opportunities were there for the taking, and their realization depended on a small number of individuals who were able to recognize and take advantage of them.

Jeff Monder ([email protected]; is director of smart grid and enterprise project management at Green Mountain Power. Over the past five years, Monder has served in key leadership roles to develop smart grid strategies, architecture and solutions, and has led initiatives that leverage new technologies and approaches to benefit electric utility customers and distribution operations in Vermont.

Steve Hadden ([email protected]), an independent  consultant to the energy industry since 1987, is a well-known expert in the smart grid technologies connecting utilities to their customers. He has supported many prominent utilities, advanced metering infrastructure suppliers and government policymakers. He was an engineering manager at GE for 15 years and holds a bachelor’s degree in engineering physics from Cornell University.

Companies mentioned:


Department of Public Safety|


Green Mountain Power|

Rural Development|

Vermont Public Service Board|


Sidebar: Gatekeeper Details

In Green Mountain Power’s deployment, gatekeepers (left box in photo) are typically located 8 ft (2.4 m) high on transformer-equipped utility poles, strategically selected to optimize the meters they can reach and to establish a reliable, resilient network. Given the environment, the customer premises equipment (right box in photo) must be able to withstand harsh winters, hot summers, and high and low humidity.

The CalAmp Fusion modem is a fourth-generation long-term evolution (4G LTE) router that supports dual radios and multi-port routing. It falls back to 2G and 3G in the absence of LTE. The device includes Wi-Fi, GPS, independent Ethernet ports, multi-wide area network (multi-WAN) switching, input/output, security and manageability. It is ruggedized to MIL-STD 810F and can operate in -40°C to 70°C (-40°F to 158°C) and 5% to 95% humidity.

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