T.L. Nelson

U.S. Department of Commerce, Washington, Washington, D.C., United States

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Publications (19)10.86 Total impact

  • T. Nelson, B. Waltrip
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    ABSTRACT: This paper describes the implementation of a quantum-based system for the generation of 120 V rms, 5 A rms, sinusoidal, active and reactive power over the 50 Hz to 400 Hz frequency range. The system relates the amplitudes and phases of the voltage and current waveforms of the generated power to a programmable Josephson voltage standard (PJVS) using a differential sampling technique. The system also employs a voltage amplifier that performs self-calibration and corrections of gain and phase errors. Details of the system design, measurement techniques, and significant sources of error are presented.
    Power and Energy Society General Meeting, 2012 IEEE; 01/2012
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    ABSTRACT: The development of a current-comparator-based system for on-site calibrations of high voltage phasor measurement unit systems will be presented. Measurement can be made under actual power system operating conditions with voltages up to 100 kV line-to-ground and currents up to 2000 A at 50 Hz or 60 Hz.
    Precision Electromagnetic Measurements (CPEM), 2012 Conference on; 01/2012
  • B.C. Waltrip, T.L. Nelson, E. So, D. Angelo
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    ABSTRACT: The results of a bilateral comparison on active/reactive power meter calibrations between the National Institute of Standards and Technology (NIST) and the National Research Council (NRC) will be presented. The comparison was implemented using a transfer standard consisting of a highly stable commercial sampling-type power/energy meter. The measurements were made at 120 V, 5A, 50 Hz and 60 Hz, at power factors of 1.0, 0.5 lead and lag, and 0.0 lead and lag.
    Precision Electromagnetic Measurements (CPEM), 2012 Conference on; 01/2012
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    ABSTRACT: A number of international comparisons of active power meter calibrations were conducted in the past. This paper addresses the international comparison of reactive power meter calibrations at 120 V, 5 A, 50/60 Hz, and power factors 0.5 lead/lag, and zero lead/lag, between 5 NMIs; 3 from the SIM metrology region (NRC, NIST, CENAM) and 2 from the APMP metrology region (NIM and KRISS).
    Precision Electromagnetic Measurements (CPEM), 2012 Conference on; 01/2012
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    ABSTRACT: We have developed a precision technique to measure sine-wave sources with the use of a quantum-accurate AC programmable Josephson voltage standard. This paper describes a differential method that uses an integrating sampling voltmeter to precisely determine the amplitude and phase of high-purity and low-frequency (a few hundred hertz or less) sine-wave voltages. We have performed a variety of measurements to evaluate this differential technique. After averaging, the uncertainty obtained in the determination of the amplitude of a 1.2 V sine wave at 50 Hz is 0.3 muV/V (type A). Finally, we propose a dual-waveform approach for measuring two precision sine waves with the use of a single Josephson system. Currently, the National Institute of Standards and Technology (NIST) is developing a new calibration system for electrical power measurements based on this technique.
    IEEE Transactions on Instrumentation and Measurement 05/2009; · 1.36 Impact Factor
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    ABSTRACT: This paper describes the implementation of a new quantum-based system for the generation of 120 V RMS, 5 A RMS, sinusoidal, active, and reactive power over the 50 to 400 Hz frequency range. The system accurately relates the spectral amplitudes and phases of the voltage and current waveforms of the generated power to a programmable Josephson voltage standard (PJVS) by using a novel differential sampling technique. The system also employs a new voltage amplifier that performs self-calibration and corrections of the gain and phase errors. Details of the system design, measurement techniques, and significant sources of error are presented.
    IEEE Transactions on Instrumentation and Measurement 05/2009; · 1.36 Impact Factor
  • IEEE T. Instrumentation and Measurement. 01/2009; 58:809-815.
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    ABSTRACT: We are developing a quantum-based 60 Hz power standard that exploits the precision sinusoidal reference voltages synthesized by a programmable Josephson voltage standard (PJVS). PJVS systems use series arrays of Josephson junctions as a multibit digital-to-analog converter to produce accurate quantum-based dc voltages. Using stepwise-approximation synthesis, the system can also generate arbitrary ac waveforms [i.e., an ac programmable Josephson voltage standard (ACPJVS)] and, in this application, produces sine waves with calculable root mean square (rms) voltage and spectral content. The primary drawback to this ACPJVS synthesis technique is the uncertainty that results from switching between the discrete voltages due to finite rise times and transient signals. In this paper, we present measurements and simulations that elucidate some of the error sources that are intrinsic to the ACPJVS when used for rms measurements. In particular, we consider sine waves synthesized at frequencies up to the audio range, where the effect of these errors is more easily measured because the fixed transition time becomes a greater fraction of the time in each quantized voltage state. Our goal for the power standard is to reduce all error sources and uncertainty contributions from the PJVS-synthesized waveforms at 60 Hz to a few parts in 10<sup>7</sup> so that the overall uncertainty in an ac power standard will be a few parts in 10<sup>6</sup>.
    IEEE Transactions on Instrumentation and Measurement 08/2008; · 1.36 Impact Factor
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    ABSTRACT: Sampling is a promising technique for comparing the stepwise-approximated sine waves synthesized by an AC Programmable Josephson Voltage Standard to the sinusoidal voltages of a secondary source at low frequencies (a few hundred hertz or less). This paper describes a differential method that uses an integrating sampling voltmeter to precisely determine the amplitude and phase of high purity sine wave voltages by comparing them to quantum-accurate waveforms.
    Precision Electromagnetic Measurements Digest, 2008. CPEM 2008. Conference on; 07/2008
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    ABSTRACT: This paper discusses measurements of the dynamic performance of electric power phaser measurement units, PMUs, and their relation to the requirements of the IEEE synchrophasor standard C37.118-2005. In particular, it proposes a new method for monitoring the dynamic power signals that change in amplitude and frequency during the testing of PMUs. The new method estimates the reference values for dynamic power signals so they can be compared with the PMU values to determine the PMU's errors. This requires estimating the "true" timestamped values of dynamic power signals with low uncertainty. The paper also discusses the issue of aliasing of sampled dynamic signals, and the relationship between the requirement in the standard to reject an out of band or interharmonic signal and dynamic signal performance.
    Hawaii International Conference on System Sciences, Proceedings of the 41st Annual; 02/2008
  • G. Stenbakken, T. Nelson
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    ABSTRACT: This paper describes the development of two test systems at NIST aimed at improving the calibration and characterization of coordinated universal time (UTC) synchronized electric power instrumentation. Reference to UTC is used to meet the need for precise time synchronization of instrumentation designed to monitor the state of the grid over its wide geographic area. The first test system is used to perform calibrations of phasor measurement units (PMUs) for parameters that have performance requirements specified in IEEE standard for synchrophasors for power systems, IEEE standard C37.118-2005. Tests performed on this system use static electric power signals. The second test system is being developed to perform dynamic tests of PMUs. This paper also describes the development of a PMU testing guideline by an industry wide task force as part of the Eastern Interconnect Phasor Project (EIPP).
    Power Engineering Society General Meeting, 2007. IEEE; 07/2007
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    ABSTRACT: We are implementing a new standard for 60 Hz power measurements based on precision sinusoidal reference voltages from two independent programmable Josephson voltage standards (PJVS): one for voltage and one for current. The National Institute of Standards and Technology PJVS systems use series arrays of Josephson junctions to produce accurate quantum-based DC voltages. Using stepwise-approximation synthesis, the PJVS systems produce sinewaves with precisely calculable RMS voltage and spectral content. We present measurements and calculations that elucidate the sources of error in the RMS voltage that are intrinsic to the digital-synthesis technique and that are due to the finite rise times and transients that occur when switching between the discrete voltages. Our goal is to reduce all error sources and uncertainty contributions from the PJVS synthesized waveforms to a few parts in 10 <sup>7</sup> so that the overall uncertainty in the AC-power standard is a few parts in 10<sup>6</sup>
    IEEE Transactions on Instrumentation and Measurement 05/2007; · 1.36 Impact Factor
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    ABSTRACT: In response to industry requests to have calibration services for distorted power instrumentation, NIST is developing a new sampling system to provide this service. This development effort is aimed at providing calibration of instruments that makes measurements in accordance with the IEEE trial use standard 1459-2000 on power measurements in distorted and unbalanced conditions. The system makes use of several NIST developed instruments and sensors.
    Power Engineering Society General Meeting, 2005. IEEE; 07/2005
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    ABSTRACT: An intercomparison of calibration systems for AC shunts up to audio frequencies (10 kHz) between the National Research Council of Canada, Japan Electric Meters Inspection Corporation, and the National Institute of Standards and Technology, is presented. The comparison was implemented with a transfer standard of 10 A, 0.1 Ω calculable AC/DC shunt, designed by Japan Electric Meters Inspection Corporation. The results indicate that there are no significant differences in the overall accuracy of calibration systems for AC shunts at frequencies up to 10 kHz in each laboratory.
    IEEE Transactions on Instrumentation and Measurement 05/2005; · 1.36 Impact Factor
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    ABSTRACT: In response to industry requests to have calibration services for distorted power instrumentation, NIST is developing a new sampling system to provide this service. This development effort is aimed at providing calibration of instruments that will make measurements in accordance with the IEEE trial use standard 1459-2000 on power measurements in distorted and unbalanced conditions. The system will make use of several NIST developed instruments and sensors.
    Power Engineering Society General Meeting, 2003, IEEE; 08/2003
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    ABSTRACT: A number of international comparisons of current transformer calibrations at power frequencies were conducted in the past. However, all comparisons were done with a secondary current output of 5 A. This inter-comparison of current transformer calibration systems for power frequencies between the National Research Council of Canada and the National Institute of Standards and Technology, USA, was done with a primary current range of 100 A and a nonstandard secondary output signal of voltage range of 10 V. The comparison was implemented with a transfer standard consisting of a commercial current-comparator-based transimpedance amplifier, based on a development at the National Research Council of Canada modified to make the output voltage adjustable in magnitude and phase within a range of ±1 percent. The results indicate that there are no significant differences in the overall accuracy of calibration systems for current transducers with a voltage output at power frequencies in each laboratory.
    IEEE Transactions on Instrumentation and Measurement 05/2003; · 1.36 Impact Factor
  • E. So, D. Angelo, T. Nelson, L. Snider
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    ABSTRACT: A number of international comparisons of power meter calibrations at power frequencies were conducted in the past, all of them being done at 120 V and 5 A. This comparison of power meter calibrations between the National Research Council of Canada and the National Institute of Standards and Technology, USA, was done to include voltage ranges up to 600 V, current ranges up to 100 A, and at power factors of 1.0, 0.5 lead and lag, and 0.0 lead and lag. The comparison was implemented by a transfer standard consisting of a modified commercial time-division multiplier type wattmeter. The results indicate that there are no significant differences in the overall accuracy of AC power measurements in each laboratory up to 600 V, 100 A, at all power factors
    IEEE Transactions on Instrumentation and Measurement 05/2001; · 1.36 Impact Factor
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    ABSTRACT: An international comparison of 50/60 Hz power is described. The traveling standard was an electronic power transducer which was tested at 120 V, 5 A, 53 Hz, at five power factors (1.0, 0.5 lead, 0.5 lag, 0.0 lead, and 0.0 lag). Fifteen national metrology institutes from six metrology regions participated in the comparison
    Precision Electromagnetic Measurements Digest, 2000 Conference on; 02/2000 · 1.36 Impact Factor
  • G. Stenbakken, T. Nelson
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    ABSTRACT: The importance of developing better tools for observing the status of the North American power grid is described. Focus is on the performance of the phase measurement units being deployed to give the raw data for this improved observability. How the availability of this information would have appeared during the August 2003 power blackout is described. IEEE is developing a standard for these units but no calibration service is available to use as a common reference to assure the interchangeability of units from different manufacturers. The program under way at NIST to develop such a calibration service and the coordination with the power industry to develop a guideline for performing these calibrations is presented. The future directions of work in this area are given
    Power Engineering Society General Meeting, 2006. IEEE;