This paper describes the basic operating principles of Phasor Measurement Units (PMUs) and their time requirements to estimate absolute phase angles. A National Institute of Standards and Technology (NIST) PMU calibration system that tests PMU performance necessary to meet the IEEE synchrophasor standard requirements is discussed. The calibration of voltage, current, and time measurements for the NIST PMU test system is described. The total vector error of the NIST PMU test system is estimated to be 0.05%. A comparison between the NIST PMU test system and a prototype commercial PMU calibrator was performed to assure traceability of relevant electrical measurements and time measurement.Index Terms-Calibration, coordinated universal time (UTC), global positioning system (GPS), phase measurement unit (PMU), total vector error (TVE), traceability, uncertainty.

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This report captures feedback from two workshops that NIST conducted to determine the challenges and opportunities in the use and design of Smart Grid Testbeds and Collaborations, which were held April 11, 2019, at the University of Tennessee, Knoxville, and April 23, 2019, at the University of Vermont. Both workshops were sponsored by the National Institute of Standards and Technology (NIST), an agency of the U.S. Department of Commerce.

Executive SummaryCorrect time and timing is one of the foundational elements in enabling the communication and orchestration of technologies for accurate and optimal wide area monitoring, protection and control (WAMPAC) in the power industry. The National Institute of Standards and Technology (NIST) and the International Electrical and Electronic Engineer -Standard Association (IEEE-SA) conducted a workshop to gather 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.One of the key drivers for the workshop is the need to prioritize NIST efforts in addressing precision timing needs in power systems. NIST has established a Smart Grid Testbed, which includes the Precision Timing module to support the IEEE 1588 Power Profile efforts and to serve as a basis for timing measurement and security research. The objective of the workshop was to identify the timing challenges, the community of experts, and potential collaborators as well as key research priorities to guide future efforts to ensuring that the integrity, availability, accuracy, and precision of timing requirements are met in power systems.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 and to reap the economic and environmental benefits of more intelligent and efficient use of generation and storage resources while meeting customer demands. The proliferation of widely deployed smart sensors for WAMPAC, distribution and energy management systems, along with the increasing need for fault detection and location as well as maintaining system stability in real time using spatio-temporal and temporalfrequency analyses, all require precision timing. These new capabilities offer increased flexibility to grid operators, but they also raise new security concerns.Among the concerns expressed include timing discontinuities such as leap seconds, Daylight Savings Time, and GPS Week Number Rollovers. Additionally, the increasing prevalence of jamming and the potential for spoofing is leading security, time and network experts in power systems or other domains to explore alternative propagation methods of traceable time. These include eLOng-RAnge Navigation (eLORAN), Iridium, IEEE 1588 Precision Time Protocol (PTP), Network Time Protocol (NTP), radio (WWVB is the NIST operated time signal radio station near Fort Collins, Colorado.), atomic clocks, and other terrestrial and satellite-based timing propagation solutions.Given the current stage of exploration and characterization for real time control, utilities and system integrators identified the top industry challenge to be integrity assurance, with the first steps being device conformance and interoperability testing, performance mo...

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