Synchrophasor Standards Testing and Certification

1. Synchrophasor StandardsTesting and Certification Allen Goldstein NIST IEEE Senior Member

2. Outline • Standards Mandated Requirements • Conformity Assessment and PMU Certification • The Role of Testing and Standards Laboratories

3. Standards Mandated Requirements

4. 21 or more PMU manufacturers • More than 50 different models of PMU • PMU functions included in “multifunction devices”: • protective relays • digital fault recorders • power quality meters • PMUs will be used in almost every power transmission system worldwide. • Each PMU has 18 or more configurations of nominal frequency (F0), reporting rate (Fs), and class (M or P) • If we do not know the limits of accuracy, how can we begin to understand how measurement errors will affect the power system?

5. IEC/IEEE 60255-118-1 Clause 5: Measurement compliance evaluation Clause 6: Measurement compliance test and evaluation This is where the actual performance limits are found Steady State Performance Unchanging magnitude and frequency Dynamic Performance Magnitude or frequency changes during the test Reporting latency • “PMU Performance shall be determined …” • Measurement evaluation • Total Vector Error (TVE) • Frequency Error (FE) • Rate of Change of Frequency Error (RFE) • Others…

6. Total Vector Error • Combines both magnitude and phase error into a single scalar value. • Scaler: it is the magnitude of the TVE line shown at the right. • Angle information of the error is lost. • This greatly simplifies comparison to some TVE limits • However, individual magnitude and phase information is lost • Since angle information is lost, cannot compare TVE values ME = magnitude error, PE = phase error

7. Frequency and ROCOF Error • Frequency Error is a signed value • The absolute value of the FE is compared to the limit • Having a signed value helps us understand the nature of the error: e.g. if it is caused by an offset in the timestamp and the frequency report and • ROCOF Error is also signed • The absolute value of the RFE is compared to the limit

8. Steady-State TVE requirements Frequency increments in 0.1 Hz steps across the range. (Up to 101 individual tests per PMU configuration) Magnitude increments of 10% Across the ranges 2nd through 50th harmonic, one at a time Interharmonics increment logarithmically so that there are more tests near the PMU Bandwidth Limit

9. Steady State Frequency and ROCOF Requirements

10. Measurement bandwidth tests show that the PMU bandwidth complies with the requirements, it can also show where the actual bandwidth ends. • It does this by successively applying magnitude or phase modulated signals in increments of 0.2 Hz modulation frequency. Dynamic Requirements:Measurement Bandwidth The limit is 3% TVE because that indicates the 3 dB “downpoint” of the frequency response has been reached. To find the actual bandwidth, continue to increment the modulation frequency until 3% TVE is reached.

11. Frequency is ramped in both direction between the bandwidth limits. • The test must only determine the performance due to ramping frequency. Since there is a ROCOF step at the beginning and end of the ramp, an exclusion interval ensures no step response is measured. Dynamic Requirements:Ramp of System Frequency Test

12. Before and after a step, for a “response time” period of 2 reports for P class or 7 reports for M class, the PMU may have an error of greater than 1% TVE • Step test ensures: • Error remains below the limit outside of the response time • The PMU measurement is properly aligned with the time stamp • Undershoot and overshoot are within limits Dynamic Requirements:Input Step Change

13. PMU Reporting Latency • The maximum difference in time between the time of the timestamp and the time the data leaves the data output port of the PMU. • This needs to be observed for the longer of 20 minutes or the time it takes for a local maxima to occur • Data output ports clocks and measurement clocks may not be synchronized and polling interval causes reporting latency to trend up or down.

14. Conformity Assessment and Certification

15. Documenting the need for PMU testing and certification • North American Synchrophasor Initiative (NASPI) Report of Task Force on Testing and Certification: • “The scope of synchrophasor technology reaches well beyond phasor measurement units (PMUs), so it would take a long time to cover the process for the entire system. It is recommended that the initial efforts should primarily focus on establishing a testing and certification process solely for PMU (performance IAW IEEE Std. C37.118.1-2011 and future amendments.” • “The guidance defined by the Testing and Certification Committee (TCC) of the Smart Grid Interoperability Panel (SGIP), summarized in this report, is highly recommended for the synchrophasor technology stakeholders to follow.”

16. NASPI Executive Summary • “It is recognized that synchrophasor technology is undergoing rapid changes and that both a PMU standard (IEEE Std. C37.118.1) and products will be undergoing changes in the near future; hence the testing and certification process is needed to make sure the new and existing products can be verified against the revised standard requirements.” • “The need for testing and certification was revealed by published test results that existing products do not meet all the requirements specified in the existing standard. This creates a level of uncertainty as to how such products will perform when used for given applications. The testing and certification process has to provide comprehensive, multi-vendor results to allow users to assess PMU performance impact on applications.” • “IEEE has initiated a PMU certification procedure for test laboratories. For IEEE to have a successful procedure and process in place, it created a Steering Committee to provide feedback from all the stakeholder groups. IEEE endeavors to adhere to the TCC recommendations for this process to succeed.”

17. IEEE Synchrophasor Performance Conformity Assessment Program • A worldwidePMU conformity assessment program. • IEEE maintains a Phasor Measurement Unit Certification Registry • Certified PMUs are tested in accordance with IEC/IEEE 60255-118-1 • Tested in accordance with the IEEE PMU Performance Test Suite Specification

18. Key elements of the Synchrophasor Conformity Assessment Program • Synchrophasor Conformity Assessment Steering Committee (SCASC) • Comprised of stakeholders from utilities, vendors, academia and government • PMU Certification Policy Document • Test Suite Specification (TSS) • Revision 3 is based on IEC/IEEE 60255-118-1 and in accordance with the Interoperability Process Reference Manual 2.0 (IPRM) • Close ties with standards setting organizations • Many SCASC members are also leading members of IEEE PSRC and IEC synchrophasor standards working groups • Test laboratories: Open invitation for PMU test laboratories to participate • Test laboratory Authorization • ICAP assesses quality and technical competence of laboratories utilizing IEC/ISO 17025 • NIST provides program traceability by using a mobile PMU Calibrator Calibration service

19. Synchrophasor Test Suite Specification (TSS) • Purpose: • Procedures and requirements for test laboratories • In accordance with the IPRM • Unambiguous test plans • Sometimes more specific than the standard to ensure all results are the same across the entire program • Scope: • IEC/IEEE 60255-118-1 • PMU Performance ONLY • Data transmission protocol (IEEE C37.118.2 or 61850) is not covered

20. Equipment needed to test PMUs • Timing reference (e.g. GPS Receiver) • Signal Source (3 phase Voltage and Current) • Signal Reference (synchrophasor, frequency and ROCOF of the sourced signal) • PMU Data receiver (TCP / UDP) • Means of comparing the PMU reports to the signal reference • Means of publishing the results.

21. PMU Test System Block Diagram

22. Jerry Stenbakken and the first NIST PMU steady state calibration system Far left: Jerry Stenbakken Middle: NIST’s first PMU dynamic test system, Far right: Fluke Calibration’s commercially available, fully automated PMU calibration system.

23. The Role of Testing and Standards Laboratories

24. 1991 2006 First PMU Tests at BPA NIST establishes the Synchrometrology Lab ONS Brazil works with Quanta Technology, NIST, Virginia Tech and BPA to perform 2005 plus dynamic testing on PMUs from different vendors IEEE 1344 First PMU standard.BPA formal test results shown at a PMU conference in DC 1995 2009 WECC Blackout report brings a new emphasis to the importance of WAMs 1996 2010 NIST ARRA grant to develop a commercially available PMU calibration system is won by Fluke Calibration BPA RFP to find utilities and vendors experiencing issues with accuracy 2002 2011 PMU standard revised, adding dynamic and latency testing 2003 2012 IEEE Conformity Assessment Program founded DOE launches the Eastern Interconnect Phasor Project PMU standard revised based on lessons learned in the lab NIST Assessment of PMU Performance and other independent lab work led to amendment to 2011 standard 2014 2005

25. ISO New England • ISO New York • PG&E • Tennessee Valley Authority • ERCOT • San Diego Gas and Electric • Duke Energy • Dominion Energy Consumers Energy becomes the first IEEE ICAP certified test lab • Georgia Tech • University of Illinois • Texas A&M University • University of Tennesseeat Knoxville • Virginia Tech • Washington State University 2015 Joint IEC/IEEE PMU standard published 2018 We cannot forget the contributions of: • Bonneville Power Administration • Consumers Energy • Electric Power Research Institute • IEEE (PES, SA, ICAP) • National Institute for Standards and Technology (NIST) • National Energy Reliability Corporation (NERC) • Oak Ridge National Laboratory • Pacific Northwest National Laboratory • ABB • Alstom • Arbiter Systems • Quanta Technology • Electric Power Group • Fluke Calibration • General Electric • Macrodyne • OSI Soft • RTDS • Schweitzer Engineering Labs • Visimax • And many others…

26. Future Roles for Testing and Standards Laboratories • Determining performance requirements for PMUs used in distribution systems • Assessing the impact of error and uncertainty propagation on applications which use data from PMUs • Additional accuracy classes • Digital Secondary System integration and influences • Generalizing synchronized measurements