by Kobi Gol, RAD Data Communications
Power utility networks are undergoing a revolution. Traditional communications infrastructure and legacy substation devices are being phased out to make way for next-generation Ethernet and Internet Protocol-based, packet-switched networks (PSNs).
Driving the transition to PSNs is the move toward smart grids. Packet transport’s high capacity is required to handle the amount of fluctuating traffic generated by the advanced grid applications envisioned in such intelligent power networks. Other drivers include the use of high-resolution Internet Protocol-based video surveillance equipment, as well as wholesale and Utelco services that provide broadband access for local businesses and service providers.
Nearly every power utility around the globe, therefore, is planning or has begun the transformation of its transmission and distribution grid into an intelligent PSN that can efficiently and reliably handle massive amounts of bidirectional or even multidirectional data communications among Internet Protocol supervisory control and data acquisition (SCADA) systems, IEC 61850 intelligent electronic devices and other substation automation equipment.
According to a 2011 Utilities Telecom Council survey, information communications technology spending by U.S. utilities was estimated at $3.2 billion on telecommunications equipment and services. Spending on transport networks represented the second-largest category, following two-way metering.
Ensuring Smart Communications Reliability
The migration to smart grid is unavoidable, but utilities, most of which operate self-owned, private networks, tend to be cautious about changes to their mission-critical communications systems. Utilities have been reluctant to migrate to Internet Protocol without proper attributes to match the deterministic behavior and high reliability of their existing circuit-based networks.
In particular, specific utility applications that require smart communications over PSNs need dependable service assurance tools to ensure low end-to-end delay, high availability and resiliency.
Packet technologies and specifically Ethernet have matured enough to include mechanisms that guarantee these required performance levels.
In recent years, concomitant with carriers’ pushing to deploy new services as revenue and growth generators, the telecom industry engineered Ethernet into a carrier-grade technology with robust performance and tight control. As a result, an extensive regime of standards has emerged to provide quality-of-service guarantees, reliability schemes and service management tools.
To slightly complicate matters, Ethernet and Internet Protocol networks are required to handle next-generation data and traffic such as analog voice, serial SCADA and teleprotection signals because extensively embedded legacy equipment will not be phased out overnight. For this purpose, utility operators have at their disposal a pseudowire emulation (PWE). PWE is the preferred method for delivering traffic between legacy devices in a packet-based environment, thus enabling them to bridge the gap between generations.
Getting the Timing Right
PSNs were not designed with built-in synchronization mechanisms and, therefore, require complementary clock transfer solutions with precision to ensure a stable network with predictable performance. In utility networks, precise timing is essential for mission-critical applications that are delay and jitter-sensitive, such as teleprotection, SCADA and power quality measurements (synchrophasors).
Until recently, GPS was used commonly to provide accurate timing. Installations of GPS antennas, however, are costly and susceptible to jamming. In place of GPS, there are several new standardized techniques for ensuring synchronization in an all-packet environment. IEC standard 61850 specifically addresses utility networks’ needs in timing and synchronization.
Multigeneration utility communication devices that support clock transfer provide substantive cost savings because they eliminate the need for costly dedicated hardware and allow accurate monitoring of synchronization performance across the power system.
Choosing the Right Packet Network
When migrating to next-gen networks, utility network operators must choose which technology to employ. Available packet-based options include carrier-grade Ethernet, Internet Protocol and flavors of multiprotocol label switching (MPLS). Each option can transport information reliably from place to place, but options have different characteristics.
Internet Protocol, for example, features a strong security protocol but lacks end-to-end operations, administration and maintenance (OAM) and protection mechanisms. MPLS has been added recently with OAM and automatic protection switching (APS) tools but has no built-in security. Carrier-grade Ethernet includes a rich tool set for both but tends to fit smaller networks better compared with large carrier backbones.
A combination of two technologies, such as an Ethernet access network with an MPLS core, offers lower cost per port, richer OAM and performance-monitoring tools and advanced protection mechanisms. It also allows GOOSE messages, a critical element in IEC 61850 substation automation deployments, to be delivered directly between substations without traversing an MPLS core, thus meeting standard performance requirements.
Or, utility operators may separate the information technology and enterprise network from the operational one. The former–used for delivering Voice over Internet Protocol (VoIP), Internet Protocol video, Internet connectivity and billing data–can benefit from the scalability of Internet Protocol/MPLS, while in the latter, carrier-grade Ethernet can replace SDH/SONET and benefit from simplified architecture and management, increased security, lower latency and assured quality of service.
Cybersecurity and PSNs
Cybersecurity also requires attention when introducing PSNs. Smart grids require a sharp increase in the number of interconnected devices, most of which are in consumer neighborhoods and homes where access is unrestricted. As a result, there are more potentially vulnerable entry points through which the grid can be disrupted. Power utility networks must employ sophisticated, scalable security measures to prevent malicious attacks.
Layering levels of protection would be effective, ideally without adding too many dedicated security appliances. Such a defense-in-depth approach should include elements such as network access control for physical authentication of the devices connecting to the network, secure inter-site virtual private network with data encryption, secure remote access, and a distributed, application-aware firewall that also validates the application logic in the communication flows between devices to protect from malicious commands.
The move toward smart grids and next-generation networks in utility communications is under way and requires utilities to give special attention to critical applications. Robust clock accuracy, quality of service assurance, resiliency and on-going performance monitoring are must-have elements in any next-generation network that is being considered by utility network operators. To meet specific utility needs and challenges, a typical smart utility communications network should include traffic management and hard/hierarchical quality of service capabilities, synchronization and security elements, as well as support for legacy services and traffic. Utilities worldwide are discovering that Ethernet has been engineered and standardized with such qualities to become carrier-grade and can meet the exacting requirements of critical utility applications.
Utilities might operate on different schedules regarding the move to smart communications, but they share the need to lower migration costs and improve efficiency and quality of service.
Kobi Gol is business development and solution manager for utilities, transportation and migration for RAD Data Communications, a manufacturer of access and backhaul equipment for data communications and telecommunications applications.