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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Precise synchronization of phasor measurements in electric power systems

Phasors representing positive sequence voltages and currents in a power network are in the most important parameters in several monitoring, control, and protection functions in interconnected electric power networks. Recent advances in computer relaying have led to very efficient and accurate phasor measurement systems. When the phasors to be measured are separated by hundreds of miles, it becomes necessary to synchronize the measurement processes, so that a consistent description of the state of the power system can be established. Global Positioning System (GPS) transmissions offer an ideal source for synchronization of phasor measurements. The concept and implementation of this technique are described. Several uses of synchronized phasor measurements are also described. Among these are improved state estimation algorithms, state estimator enhancements, dynamic state estimates, improved control techniques, and improved protection concepts.

Phadke, Arun G.↗
NASA NTRS1991

Precise time dissemination and applications development on the Bonneville Power Administration system

The Bonneville Power Administration (BPA) uses IRIG-B transmitted over microwave as its primary system time dissemination. Problems with accuracy and reliability have led to ongoing research into better methods. BPA has also developed and deployed a unique fault locator which uses precise clocks synchronized by a pulse over microwaves. It automatically transmits the data to a central computer for analysis. A proposed system could combine fault location timing and time dissemination into a Global Position System (GPS) timing receiver and close the verification loop through a master station at the Dittmer Control Center. Such a system would have many advantages, including lower cost, higher reliability, and wider industry support. Test results indicate the GPS has sufficient accuracy and reliability for this and other current timing requirements including synchronous phase angle measurements. A phasor measurement system which provides phase angle has recently been tested with excellent results. Phase angle is a key parameter in power system control applications including dynamic braking, DC modulation, remedial action schemes, and system state estimation. Further research is required to determine the applications which can most effectively use real-time phase angle measurements and the best method to apply them.

K. E. Martin↗
NASA NTRS1996

Bonneville, Power Administration Timing System

Time is an integral part of the Bonneville Power Administration's (BPA) operational systems. Generation and power transfers are planned in advance. Utilities coordinate with each other by making these adjustments on a timed schedule. Price varies with demand, so billing is based on time. Outages for maintenance are scheduled to assure they do not interrupt reliable power delivery. Disturbance records are aligned with recorded timetags for analysis and comparison with related information. Advanced applications like traveling wave fault location and real-time phase measurement require continuous timing with high precision. Most of BPA is served by a Central Time System (CTS) at the Dittmer Control Center near Portland, OR. This system keeps time locally and supplies time to both the control center systems and field locations via a microwave signal. It is kept synchronized to national standard time and coordinated with interconnected utilities. It is the official BPA time. Powwer system control and operation is described, followed by a description of BPA timing systems including CTS, the Fault Location Acquisition Reporter, time dissemination, and phasor measurements. References are provided for further reading.

Martin, Kenneth E.↗
NASA NTRS2007

Roller Bearing Health Monitoring Using CPLE Frequency Analysis Method

This paper describes a unique vibration signature analysis technique Coherence Phase Line Enhancer (CPLE) Frequency Analysis - for roller bearing health monitoring. Defects of roller bearing (e.g. wear, foreign debris, crack in bearing supporting structure, etc.) can cause small bearing characteristic frequency shifts due to minor changes in bearing geometry. Such frequency shifts are often too small to detect by the conventional Power Spectral Density (PSD) due to its frequency bandwidth limitation. This Coherent Phase Line Enhancer technology has been evolving over the last few years and has culminated in the introduction of a new and novel frequency spectrum which is fully described in this paper. This CPLE technology uses a "key phasor" or speed probe as a preprocessor for this analysis. With the aid of this key phasor, this CPLE technology can develop a two dimensional frequency spectrum that preserves both amplitude and phase that is not normally obtained using conventional frequency analysis. This two-dimensional frequency transformation results in several newly defined spectral functions; i. e. CPLE-PSD, CPLE-Coherence and the CPLE-Frequency. This paper uses this CPLE frequency analysis to detect subtle, low level bearing related signals in the High Pressure Fuel Pump (HPFP) of the Space Shuttle Main Engine (SSME). For many rotating machinery applications, a key phasor is an essential measurement that is used in the detection of bearing related signatures. There are times however, when a key phasor is not available; i. e. during flight of any of the SSME turbopumps or on the SSME High Pressure Oxygen Turbopump (HPOTP) where no speed probe is present. In this case, the CPLE analysis approach can still be achieved using a novel Pseudo Key Phasor (PKP) technique to reconstruct a 1/Rev PKP signal directly from external vibration measurements. This paper develops this Pseudo Key Phasor technique and applies it to the SSME vibration data.

Jong, Jen-Yi↗
NASA NTRS1990

State estimation for spacecraft power systems

A state estimator appropriate for spacecraft power systems is presented. Phasor voltage and current measurements are used to determine the system state. A weighted least squares algorithm with a multireference transmission cable model is used. Bad data are identified and resolved. Once the bad data have been identified, they are removed from the measurement set and the system state can be estimated from the remaining data. An observability analysis is performed on the remaining measurements to determine if the system state can be found from the reduced measurement set. An example of the algorithm for a sample spacecraft power system is presented.

Williamson, Susan H.↗
NASA NTRS1996

Wideband Interferometric Sensing and Imaging Polarimetry

Wideband Interferometric Sensing and Imaging Polarimetry (WISIP) has become an important, indispensible tool in wide area military surveillance and global environmental monitoring of the terrestrial and planetary covers. It enables dynamic, real time optimal feature extraction of significant characteristics of desirable targets and/or target sections with simultaneous suppression of undesirable background clutter and propagation path speckle at hitherto unknown clarity and never before achieved quality. WISIP may be adopted to the detection, recognition, and identification (DRI) of any stationary, moving or vibrating targets or distributed scatterer segments versus arbitrary stationary, dynamical changing and/or moving geo-physical/ecological environments, provided the instantaneous 2x2 phasor and 4x4 power density matrices for forward propagation/backward scattering, respectively, can be measured with sufficient accuracy. For example, the DRI of stealthy, dynamically moving inhomogeneous volumetric scatter environments such as precipitation scatter, the ocean/sea/lake surface boundary layers, the littoral coastal surf zones, pack ice and snow or vegetative canopies, dry sands and soils, etc. can now be successfully realized. A comprehensive overview is presented on how these modern high resolution/precision, complete polarimetric co-registered signature sensing and imaging techniques, complemented by full integration of novel navigational electronic tools, such as DGPS, will advance electromagnetic vector wave sensing and imaging towards the limits of physical realization. Various examples utilizing the most recent image data take sets of airborne, space shuttle, and satellite imaging systems demonstrate the utility of WISIP.

Verdi, James Salvatore↗
NASA NTRS2003

Phasor algorithms of the SIM fringe estimation

The Space Interferometry Mission (SIM) will provide unprecedented micro-arcsecond (pas) precision to search for extra-solar planets and possible life in the universe. SIM will also revolutionize our understanding of the dynamics and evolutions of the local universe through hundred-fold improvements of inertial astrometry measurements. SIM has two so-called guide interferometers to provide stable inertial orientation knowledge of the baseline, and a science interferometer to measure target fringes. The guide and science measurements are based on the fringe phase measurements using a CCD detector. One of the key issues with SIM is to develop a new algorithm for calculation of fringe parameters. Not only astrometric results need that new algorithm, but also real-time fringe tracking requires a new method to calculate phase and visibility fast and accurately. The formulas for the phasor algorithms for fringe estimation are presented. The signal-noise ratio performances of the fringe quadratures are demonstrated. The advantages of phasor algorithms for application of fast fringe tracking and on-board data compression are discussed.

interferometry↗
NASA NTRS1987

Comparison of measured and calculated forces on the RE-1000 free-piston Stirling engine displacer

The NASA Lewis Research Center has tested a 1 kW free-piston Stirling engine at the NASA Lewis test facilities. The tests performed over the past several years on the RE-1000 single cylinder engine are known as the sensitivity tests. This report presents an analysis of some of the data published in the sensitivity test report. A basic investigation into the measured forces acting on the unconstrained displacer of the engine is presented. These measured forces are then correlated with the values predicted by the NASA Lewis Stirling engine computer simulation. The results of the investigation are presented in the form of phasor diagrams. Possible future work resulting from this investigation is outlined.

Schreiber, Jeffrey G.↗
NASA NTRS1988

Development and experimental test of an analytical model of the orifice pulse tube refrigerator

An analytical model for the orifice pulse tube is developed, in which the system is described in terms of average enthalpy flow with such simplifying assumptions as an ideal gas and sinusoidal pressure variation. Phasor analysis is used to represent temperature, pressure, and mass-flow rate waves in vector form. The model predictions, namely, that the refrigeration power of a pulse-tube refrigerator is proportional to the average pressure, the pulse frequency, the mass-flow ratio, and the square of the dynamic pressure ratio, were verified by experimental measurements. It was found that, as a result of the simplifying assumptions, the magnitudes of the refrigeration power predicted by the model were between three and five times greater than experimental values.

Storch, Peter J.↗
NASA NTRS1991

Suppressing interfering scattered signals in swept-frequency radar measurements by using frequency domain Wiener filtering

A novel approach to the reduction of scattered, interfering signals that corrupt measurements of the signal backscattered from radar targets of interest is being developed. It is being explored with sphere measurements in an indoor microwave radar range. This method is based on the concept of Wiener filtering (which minimizes the difference between the signal plus noise and the desired signal in the time domain). In contrast to the traditional Wiener filter, in which the time domain error between two sequences are minimized, the approach reported uses the frequency domain phasor amplitudes of a swept frequency signal. It minimizes the difference (least-mean-square-magnitude) between the signal-plus-noise and the signal complex phasors, across the entire spectrum.

Weissman, David E.↗