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Unformatted text preview: 0-7803-8465-2/04/$20.00 2004 IEEE. Comparative Testing of Synchronized Phasor Measurement Units Juancarlo Depablos Student Member, IEEE Virginia Tech Virgilio Centeno Member, IEEE Virginia Tech Arun G. Phadke Life Fellow, IEEE Virginia Tech Michael Ingram Member, IEEE Tennessee Valley Authority Abstract This work reports the result of a comparative testing done on four Phasor Measurement Units ( PMU ) from different manufacturers. Phase shift and attenuation at fundamental frequency, performance under system balanced and unbalanced conditions and performance under system variable frequency are the issues addressed for this comparative assessment. The results are presented in a comparative evaluation of features and performance of the PMU units. The results of this work reveal that data from the tested PMU units is of comparable accuracy only under nominal frequency operating conditions. At off- nominal frequency operation every tested PMU unit yielded a different phase and magnitude for the common measured voltage signal. The existing Synchrophasor standard does not specify phase or magnitude performance for off-nominal frequency operation. The standard is in the process of revision, and it is expected that the revised standard will specifically address performance requirements at off-nominal frequencies. Introduction Phasor Measurement Units (PMUs) are among the most interesting development in the field of real-time monitoring of power systems. PMU units provide real- time measurement of positive sequence voltages and currents at power system substations. Typically the measurement windows are 1 cycle of the fundamental frequency, and the measurements are time-stamped to a common GPS time synchronization signal. Data from substations are collected at a suitable site, and by aligning the time stamps of the measurements a coherent picture of the state of the power system is created. Many applications of these measurements have been described in the literature. Several algorithms can be used to estimate the magnitude and phase of currents and voltages; however, one of the most extensively used by PMU manufacturers is the Fourier filter because of its harmonic rejection property and estimation speed, as well as its recursive formulation . Although the basis of the Synchronized Phasor Measurement may be the same for every PMU unit in the market, the implementation of the measurement algorithm may be rather different between PMU units. Manufactures are free to chose variables such as measurement window size, sampling rate, time stamping and phasor computation rate to suit the standard measurement algorithm to its particular hardware requirements and/or limitations in order to achieve maximum precision of measurement. These differences in the implementation of the phasor measurement algorithm may lead to differences among PMU units of different manufactures, which would jeopardize mix-and-match application of these PMU units. For instance, precision of application of these PMU units....
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This note was uploaded on 01/29/2011 for the course ENGR 52 taught by Professor Mcmillan during the Spring '10 term at Baylor Med.
- Spring '10