BY HOWARD SELF AND ADAM GUGLIELMO, ABB INC.
We’ve all heard the buzz about IEC 61850, the global design standard for substation automation. But how much truth is there to these claims? This question was on the mind of the operations manager of a municipal utility when he visited the ABB Smart Grid Center of Excellence (CoE) in Raleigh, N.C. He was considering developing a smart grid substation standard design using IEC 61850.
He began his investigation into IEC 61850 by attending seminars, participating in webinars and asking suppliers about functionality within the standard. The utility’s preferred vendor at that time had questioned the preference for IEC 61850 and commented that the standard might not support all of their requirements. This was the catalyst for visiting the CoE. He wanted to determine whether the IEC 61850 standard is all hype or could meet their requirements. Figure 1 illustrates a simplified layout of the desired substation automation architecture.
His utility takes delivery on its distribution system from a large investor-owned utility and manages both 23-kV and 4-kV distribution from 10 substations with a small technical group responsible for protection, control, load management and communications. The city council approves budgets, and efficiency and reliability infrastructure investments must show a quick, positive return. The manager’s goals were to monitor, measure, control, report, diagnose, resolve and restore efficiently when system events occur. The municipal envisions a broadband network that uses fiber and wireless mesh communications throughout the system. Longer-term goals include automatic fault detection, isolation and restoration (FDIR) on all feeders and coordination of the load management system with substation voltage regulators’ shaving peak demand without sacrificing quality or reducing much needed revenue to the municipal.
As seen in Figures 1 and 2, IEC 61850 employs Ethernet only as its communication medium, thereby reducing the number of connections required to each intelligent electronic device (IED), computer or both and allowing high-speed access to every device within the network from any secure remote access point. Each device can be time-synchronized from redundant Simple Network Time Protocol (SNTP) time servers and reduce the need for local time servers at each location. Communications redundancy is illustrated in Figures 1 and 2, but redundancy is supported in multiple forms. For example, traditional supervisory control and data acquisition (SCADA) has relied on remote terminal units (RTUs) and data concentrators to connect to IEDs, meters, transducers and substation I/O. The RTU would normalize the substation data and then transmit it to the SCADA master when queried. Then, one SCADA master shares its data with a backup master or the RTU can report data to multiple masters. This has been effective, but more efficient tools based on the IEC 61850 standard are available. This reduces the management of multiple systems and databases and eliminates a single point of failure such as the RTU, data concentrator at the substation or both.
The COE has a substation automation system similar to the configuration the municipality was considering, except the CoE uses high-speed wireless networks for all IED connections downstream from the substation. The visitor wanted a demo to access an IED via the network using hardwired and wireless connections for IED configuration and monitoring, monitoring of Generic Object Oriented Substation Events (GOOSE) messages between IEDs and accessing the IEC61850-8-1 clientserver data and a SCADA system. The primary concern of the technical team was the ease of viewing, observing and troubleshooting devices. Rather than demonstrate this functionality, we allowed our visitor to access the network control center client computer to observe from the control center down to the IED level. Once logged into the IED, in this example ABB REF615_12, using a standard browser, (e.g., IE, Firefox or Chrome), the IED status was apparent. The real-time sequence of events from the IED equipped with a secure Web server can be seen in Figure 3. The IED configuration tool then was opened from the same computer and events from the ABB PCM software were viewed and compared with the Web browser at the control center as in Figure 4. This convinced our visitor that the technical team, using a standard for Ethernet, could access an IED quickly and easily, determine device functionality and understand the system.
|Real-time Events From IED With Secure Web Server|
|ABB PCM and Control Center Comparison|
The substation computer verified information at the control center and substation were consistent. Again, we accessed both the station one-line and communication statistics of the IED (see Figures 5a and 5b) using a standard browser from the same computer, which enabled quick and efficient data comparison at the IED, substation and control center levels.
|5 Data Comparison at the IED, Substation and Control Center Level|
Next, it was important to show what other diagnostics were available within the IEC 61850 standard to help determine the status of the circuit breaker controlled by the IEDs. We used a standard IEC browsing tool over a secure connection, and the circuit breaker model CXCBR1 in the IED was easily viewable from the browser. To demonstrate flexibility of the standard, a third-party tool was used to look into the IEC 61850 models in the IED and drill down to specific objects’ status. In Figure 6, breaker health (health=1, Normal), breaker position (1,0=Open), life cycle operation counter (14), breaker operating capability or switching energy (CBO Cap=3, charged for close-open operation) and verification that nothing was blocking the open or close operation (Blkopn=F, BlkCls=F) were determined quickly and efficiently. Monitoring of horizontal communications allows us to determine the interaction between devices. From the same control center operator terminal, this information was accessed using the SOE log in the IED, WireShark, Omicron Scout and ABB’s ITT600 SA Explorer. Figure 7 shows graphical, tabular and statistical views of horizontal message network traffic, which is interpreted easily by any user. After the ease of access to real-time information, one question remained: How easy is device management with IEC 61850? A demonstration of the system configuration tools as defined by the standard validated that the IEC 61850-defined object models provide efficient, accurate and consistent access, configuration and maintenance of the system. The need to understand single-point addresses as required by traditional protocols is eliminated.
|Horizontal Message Network Traffic|
Communication no Longer Limiting Factor
With Ethernet advancements, communications is no longer a limiting factor inside or outside substations. Access to information over long distances is possible securely and cost-effectively. Wireless communications lends itself to quick and comparatively inexpensive deployments across wide areas such as a utility distribution grid, but utilities must pay careful attention to several factors that will impact directly their ability to achieve the IEC 61850 vision.
One network, many applications. The network must be able to support multiple applications and must provide broadband capacity to ensure future demands are satisfied. Beyond just capacity, though, the networking equipment should be able to create multiple virtual local-area networks (VLANs) in the event there is a need to segregate certain types of traffic within the network. Furthermore, the network should have rich quality of service capabilities to ensure the most mission-critical traffic is handled accordingly.
Reliability. Utilities should be looking at technologies that provide four or five nines of reliability and should be wary of single points of failure in their network design. Similarly, when relying on public networks, utilities should carefully examine their service level agreements to determine what service levels are guaranteed during emergencies. Generally, this is when information and control regarding field assets are most critical, so this is not when communications networks should fail. Technology choices including wireless mesh that allow for quick and automated reconfiguration among multiple paths can help improve reliability.
Low latency. Certain applications, such as automated fault detection isolation and restoration, have low tolerance for delay. Communication networks must support the requirements of all deployed applications, so low-latency capability is essential in evaluating communications technology.
Security. As utilities seek to enable the benefits of IEC 61850 and modern networking, they also must protect their systems from misuse. Utilities should look for communications networks that incorporate tested and proven security mechanisms in the enterprise networking world. Specifically, can the network provide secure communication paths among assets in the field and the centralized management infrastructure? Can the technology control which devices, protocols and applications are allowed access to the network?
Our visitor was satisfied with the performance and ease of access to real-time data enabled by the IEC 61850 architecture. He said that the engineering definition and structure defined in the standard will simplify engineering and integration for the technical team. He was convinced that building a system on the foundation of the IEC 61850 standard would more than satisfy the goals of increased operational efficiencies, maximized system interoperability and support for implementation of advanced applications, which will ensure long-term system viability.
Howard Self is the program manager for the ABB Smart Grid Center of Excellence.
Adam Guglielmo is the business development director for ABB Wireless Communication Systems (formerly Tropos Networks).