By Aaron Martin, Bonneville Power Administration (BPA), and Bob Noseworthy, University of New Hampshire InterOperability Laboratory (UNH-IOL)
For the power industry, correct time and timing is essential in enabling the communication and orchestration of technologies for accurate and optimal wide area monitoring, protection and control (WAMPAC). Today, advancements in smart grid technologies are providing new capabilities and increased flexibility for grid operators, but also raising new security concerns. A co-hosted workshop of the National Institute of Standards and Technology (NIST), the IEEE Standards Association (IEEE-SA) and the University of New Hampshire Interoperability Lab (UNH-IOL) gathered inputs from stakeholders to identify, analyze and provide guidance on technologies, standards and methodologies for addressing the practical timing challenges that are currently being experienced in wide area time synchronization.
Topping the list of challenges faced by utilities and system integrators is integrity assurance, with the first steps being device conformance and interoperability testing, performance monitoring and timely detection of any potential anomalies. These issues point to a real need for robust conformance and interoperability test methods to provide a degree of assurance that reference time can be properly distributed and that devices can synchronize to a required degree of accuracy as defined by industry. What’s more, system end-to-end interoperability and performance testing also provide assurance that the time distribution across multiple devices from various manufacturers can meet industry specifications.
With the emerging use of Ethernet for intra-substation communications, in 2008 the IEEE introduced the C37.238-2008 time-distribution protocol (eliminating the need for the traditional IRIG-B dedicated-wiring time-distribution links); the latest revision is IEEE C37.238-2017. To mitigate these inter-vendor interop issues, a TSS (Test Suite Specification) has been generated from collaborative efforts of the IEEE Conformity Assessment Program (ICAP), NIST and UNH-IOL, who have established a pilot conformity test program based on the NIST TSS for IEEE C37.238, IEEE Standard Profile for Use of IEEE 1588 Precision Time Protocol in Power System Applications, with the goal of establishing a certification process for device manufacturers provisioning the power generation and distribution market space. Released in late 2017, IEEE C37.238 specifies an extended common profile for the use of IEEE 1588, IEEE Standard for a Precision Clock Synchronization Protocol for Networked Measurement and Control Systems, in power system protection, control, automation and data communication applications utilizing Ethernet communications architectures. It is compliant with both the core Ethernet time-distribution standard, IEEE 1588-2008 (=IEC 61588:2009), and the base Power Profile standard, IEC/IEEE 61850-9-3:2016, with special attention given to ensuring consistent and reliable time distribution within substations, between substations and across wide geographic areas.
ICAP develops and implements programs that couple standards development activities with conformity assessment activities in order to accelerate market adoption, while reducing implementation costs.
Power Grid Timing Challenges
Precision timing synchronization with requirements ranging from one microsecond to hundreds of nanoseconds within and across substations is currently being characterized and monitored by utilities, in order to advance capabilities in real-time measurement and control. In doing so, they are working to reap the economic and environmental benefits of more intelligent and efficient use of generation and storage resources while meeting growing customer demands. The proliferation of widely deployed smart sensors for WAMPAC in distribution and energy management systems, along with the increasing need for fault detection and location, as well as maintaining system stability in real time, all require precision timing.
According to Ravi Subramaniam, IEEE Conformity Assessment Program Technical Director, “Today, power system applications require high precision time synchronization in order to meet the challenges associated with device interoperability, responding to network failures, and delivering consistent and reliable time distribution within substations, between substations and across wide geographic areas.”
In the U.S. power grid, where each interconnection stretches over a large geographical area, achieving correct timing can be challenging. Time distribution issues include resolving multiple time scales, Global Navigation Satellite System (GNSS) receiver performance, packet delay variations in the communication infrastructure and cyber-physical security, as well as concerns for reliability and resilience when a reference source becomes unavailable or unreachable.
“IEEE is committed to supporting standards development with conformity assessment activities. The work we’ve done with our partners will bolster IEEE standards adoption for power generation and distribution and establishes a framework for certification that can enable more secure and robust grid functionality,” says Subramaniam.
The growing importance of timing in power grid applications opens up new security concerns, such as the impact of timing errors among devices having the potential to be misinterpreted as power system disturbances. Actual events demonstrated how measurement devices’ GPS receivers locked to a single satellite led to the loss of two 500 kV transmission lines. Such incidents demonstrate why it’s imperative that advanced grid automation capabilities have assured integrity of timing and of measurement.
One of the most significant timing challenges is the ability to provide sub-microsecond synchronization, or in some cases, hundreds of nanoseconds, over large geographical areas. With GNSS as the primary source, the technology can be susceptible to intentional and unintentional interference due to the low power signal propagation. Well-established security concerns include the increased use of personal privacy devices (jammers) and the potential for spoofing of GNSS signals. Unfortunately, alternative solutions to GNSS are few and costly.
“Emerging smart grid systems require secure, reliable and precise timing and synchronization to accommodate the growing diversity in resources, actors and operations,” said Christopher Greer, Director of the Smart Grid and Cyber-Physical Systems Program Office at NIST and National Coordinator for Smart Grid Interoperability. “The new Test Suite Specification, developed with experts from industry, academia and government, emerges from a continuing collaboration between UNH-IOL, NIST and IEEE, and provides the conformance and interoperability testing capabilities that supports effective adoption of precision timing standards and needed assurance on products and devices being deployed in the smart grid.”
The newly developed TSS demonstrates the effectiveness of working collaboratively with industry, academia and government on research and standards development that can advance smart grid technologies with an emphasis on interoperability and security. Such ongoing efforts ensure that the smart grid will continue to advance in a manner where future applications can overcome time and timing challenges to become more resilient, dynamic and responsive and enable more efficient and responsive operability for a smart energy future.
Aaron Martin received a BSEE from University of Idaho in 2000, and a MEEE from the University of Idaho in 2007. He is licensed professional engineer in the state of Washington and a Main Committee Member of the Power System Relaying Committee of the IEEE. In 1999, Aaron Martin began work for the Army Corp of Engineers as a Maintenance Engineer at Lower Granite Dam, located on the Snake River, in Washington State. In 2002, he left the USACE to work for the Bonneville Power Administration as a System Protection Field Engineer in The Dalles, Oregon. In 2006, he transferred to BPA’s Branch of System Protection and Control in Vancouver, Washington. His main duties involve system protection issues on 115kv, 230kv and 500kv transmission systems. Aaron currently serves as chair of the IEEE 1588 Power Profile Conformity Assessment Program steering committee.
Bob Noseworthy is the Chief Engineer at the University of New Hampshire InterOperability Laboratory (UNH-IOL). In this role, he advises on and leads various technical development activities such as TSN-related Testing Services, Avnu Alliance’s Certification, Automotive Networking, Industrial Networking, Pro AV Networking, and IEEE 1588/PTP Test Services. He is also closely involved with Test Suite Specification development for IEEE C37.238-2017 (IEEE 1588 Power Profile), the continued evolution of 802.1’s Time Sensitive Networking standards (formerly Audio/Video Bridging), as well as continuously evolving areas such as Open Fabrics Alliance logo program, and Ethernet Fabrics.