Hybrid Communication Networks—The Key to Meeting Smart Grid Requirements


Ken Monro, S&C Electric Co.

Government stimulus funding for the smart grid has attracted suppliers from other industries who are intent on repurposing their products to capture new business.

Because communication is a key enabler of smart grid applications, offerings based on technologies such as WiMAX, 802.11, mesh protocols, and 3G are flooding the marketplace. The myriad of choices often are accompanied by mixed messages regarding these products’ capabilities.

In many ways the state of the utility marketplace is analogous to the 1990’s telecom revolution. Then, the demand for applications such as data networking drove a shift from the switched cir-cuit-based networks that had been in place for decades to packet-based, all-IP networks. That convergence created a completely new way of thinking and working. In the short term, it made designing systems more difficult. Groups with projects that had been autonomous suddenly were required to collaborate across multiple departments.

Understanding Everyone’s Requirements is Essential

Stimulus funding has created a gold rush mentality. Suppliers are entering the electric utility marketplace armed with products not specifically designed for electric utility applications. Suppliers frequently claim their offerings can meet rigors of the electric utility environment, but they lack an in-depth understanding of the requirements. Many offerings have a place in the grid, but evaluating them is difficult because they haven’t been tested properly for electric utility applications.

Supporting protocols such as distributed network protocol (DNP) appears straightforward to new market entrants until they understand the sensitivities of electric utility networks. This can lead to a situation in which a utility deploys a network that requires additional testing and develop-ment by the communications supplier to support the primary application effectively.

The smart grid regulatory environment is complex and evolving rapidly with concerns such as cybersecurity. Utilities need a solution that can meet current and future requirements and a partner committed to their long-term needs.

Consider the next-generation wireless solutions being developed to carry worker productivity, metering and distribution automation traffic. These solutions must meet a diverse set of regulatory requirements in addition to the needs of several departments within utilities. Each department must understand the others’ requirements in rolling out such systems.

There is NoSingle Solution

Designing and building communication networks has always been complicated. It’s even more so now with diverse applications coexisting on the same network architecture. Today’s challenges require a wide view of the options and a deep understanding of stakeholders’ needs. It requires an open mind to find the right balance among reliability, cost, throughput, range, coverage and, increasingly, security. No single communication technology meets all the needs. Rather, integrating the best tools will create an effective solution for requirements now and in the future.

One area that provokes discussion is the use of public network resources such as cellular service vs. deploying privately owned networks. Some people think a utility must have total control over this critical infrastructure to ensure reliability and availability. Others think network operators know more about communications than utilities.

A place exists for both approaches. In the public safety market, for example, most organizations take advantage of convenient public cellular networks but also deploy a private network for essential communications and as insurance in case the public network is unavailable.

For years electric utilities have used utility-specific protocols on proprietary communication networks. This has worked reasonably well, and many don’t see the need to change it. But this view isn’t broad enough when evaluating the next generation of communications. Because many networks deliver usable bandwidth of less than 50 kilobits per second (kbps), they might be unable to support application traffic other than straight supervisory control and data acquisition (SCADA) or advanced metering infrastructure (AMI) as the requirements of encryption increase and some of the network throughput becomes dedicated to encryption protocols such as Data Encryption Standard (DES) and Advanced Encryption Standard (AES).

The telecom revolution has shown that a standards-based approach is the best way to take advantage of innovation and supplier competition that will come from the device ecosystem and applications development community. Security compliance likely will benefit from the development community’s efforts.

NIST 800-53 recommends security controls for federal information systems and organizations. It’s a complex set of guidelines that utilities must use to establish theirsecurity requirements or face potential penalties. The scenario is daunting, considering the many ways in which these guidelines could be interpreted and implemented relative to a given application. Because of vary-ing requirements across applications, utilities must deploy the right products in the appropriate areas of the overall communication architecture. According to a recent Utilities Telecom Council report, the Cyber Security Coordinating Task Group showed what needed to be secured but gave almost no guidance on how it needed to be secured. Because of the large development community, deploying an all-IP network offers the best means for adapting to these evolving requirements.

Licensed vs. unlicensed options also must be considered. For example, in many markets, 3.5 GHz is a licensed solution. But in diverse terrains, physics often make it necessary to use unli-censed equipment in the 900-MHz range to provide contiguous coverage. Unlicensed products have been engineered to survive and thrive and offer a powerful complementary network option. The situation can get complicated in markets such as the U.S., where exclusion zones can limit the areas in which a single frequency such as 3.65 GHz can be used. A mix of licensed and unlicensed equipment can deliver the best solution.

An area often overlooked is the physical integration of the communication device with the utility control and the deployment environment. Many products that have proven adequate for deploy-ment in applications such as public safety might need to be modified to meet utility requirements. Differences in the type of power source required, serial support and the need for battery backup can create a situation in which a device requires external power, media converters and batteries for electric grid deployment. This introduces additional costs, complexity and points of failure.

Building a Network of Networks—Hybrid Communication Architecture

S&C Electric Co. is a strong proponent of a hybrid communication architecture for the wide-area network (WAN) because it provides the necessary low-latency, peer-to-peer connectivity needed for distribution automation applications such as automatic service restoration. Hybrid communication also offers the benefits of a standards-based network for applications such as AMI and worker productivity.

The hybrid approach uses the right tools for the job, leveraging standards such as Internet proto-col (IP) and simple network management protocol (SNMP) to create an optimized, interoperable network solution unified by a common management system. Many communication technologies have a place in the network, but users must comprehensively evaluate these technologies’ capa-bilities vs. each application’s requirements.

Recently, S&C Electric Co. developed a hybrid communication solution for a major electric utility’s WAN, combining the benefits of WiMAX in the licensed 3.65-GHz spectrum with a mesh network in the unlicensed 900-MHz spectrum. The integrated private network solution enabled the customer to realize the benefits of each technology, plus the interoperability of an all-IP solution.

The network employs WiMAX for wide-area wireless connectivity, integrated with an S&C SpeedNET radio network that handles distribution automation traffic and provides AMI back-haul in gaps in the WiMAX coverage area, such as wooded areas and government-defined exclu-sion zones. The solution provides the necessary low-latency, peer-to-peer connectivity needed for automatic service restoration, plus the benefits of a standards-based network.

WiMAX is excellent for providing wireless data connectivity over a wide area. It is a high-site solution installed on a tower and offers specific coverage area around that tower. Because it is a standard, opportunities exist to ride the cost-reduction curve over time based on an increasing customer base. It is a proven system and provides connectivity for hundreds of thousands of consumers around the world.

But challenges exist in applying a single wireless technology such as WiMAX. In fringe areas, there may be solid connectivity at one point and no connectivity a few dozen feet away. Deploying a complementary, lower-frequency technology can address these gaps for AMI backhaul and distribution automation applications.

Because both networks are IP-based, equipment can be deployed across the network in a plug-and-play fashion. AMI backhaul and DA traffic can be applied on the same network, maximizing the utility’s return on investment while ensuring that critical system-protection traffic is given the highest priority. And because both networks are SNMP-based, they easily can be integrated into a network management system that gives the customer a portal into the entire network.

Smart grid applications present a diverse set of requirements that will continue to evolve. A stan-dards-based hybrid architecture is the only effective way to provide a future-proof solution. Elec-tric utilities can benefit from a partner that understands power grid application requirements. They need a supplier that has the breadth of products and the depth of knowledge and experience to help them successfully navigate the challenge.

Monro is vice president of communications systems at S&C Electric Co.

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