Measurements Of Line Parameters Research Articles

Measurement Uncertainty Evaluation of Transmission Line Parameters

Transmission line parameters vary with environmental and operating conditions, thus introducing uncertainties in power flow studies and protection zone settings of relay protection equipment. Variations in line parameters are fundamental for the determination of static and dynamic line power ratings. Usually, nominal values are given without an associated confidence interval, and therefore an important piece of information is missing. With the proliferation of phasor measurement units (PMUs) that allows for synchronized measurements at different geographical positions arouse the possibility for simple and efficient measurements of line parameters. This article analyzes uncertainties associated with the estimation of line parameters, based on the equivalent $\pi $ model, valid for short-and medium-length transmission lines. This problem has been addressed in literature, but only from a theoretical perspective and the obtained results were verified with simulations only. Here, measurements conducted on two 220-kV transmission lines are analyzed. It was found that the correlation between voltage and current measurements must be taken into consideration when analyzing uncertainty propagation law. Only then statistical analysis of estimations matches the predictions obtained by applying the theoretical model. Accuracy limits were analyzed as well, but in this case some results were within the calculated limits, while others did not follow predictions. Improvements in accuracy limits’ determination require the separation of environmental and operating condition variations from deviations due to measurement equipment, thus requiring additional information.

Temperature-dependent line parameter study of acetylene transitions near 3 µm

Knowledge of the acetylene spectrum is important for astrophysics, atmospheric, and combustion chemistry research. Twelve acetylene transitions across eleven bands have been studied between 3335.0 and 3336.5 cm−1 with a tunable interband cascade laser. Linestrengths and temperature-dependent lineshape parameters, including collisional broadening and narrowing, are reported through Voigt, Rautian, and Galatry lineshape fits to two strong cold band transitions. Measurements were made in pure acetylene, as well as with diluents argon, nitrogen, and methane, over a temperature range of 296–637 K and pressures of 5–90 Torr. Linestrengths and temperature-dependent self-broadening coefficients are also reported for ten weak hot band transitions through Voigt lineshape fits, measured between 296–513 K and 5–20 Torr. Line parameter measurements are found to be in good agreement with the literature and extend experimental lineshape studies of acetylene into new rovibrational bands, a sparsely-studied temperature regime, and a new perturber: methane.

Establishing parameters of very high voltage power lines for various loadings and atmospheric conditions

The idea of establishing parameters of electro-power system elements under real conditions of work, and therefore of very high voltage power lines, was suggested at CIGRE congress of 1972. In Romania, I undertook the work on this applied research. In the classical theory of the symmetrical quadrupole of a very high voltage power line, it was considered known its uniform distributed parameters and the magnitudes of its input values and its output values unknown. The problem arising is to determine its internal parameters when the input and output values are known. It was necessary to develop an adequate mathematical method for this purpose, and in the first part of the article I present it in detail. The article presents an adequate way of measurement to reach this purpose, as well as the necessary cautions to do away with the possible errors of measurement, and a synthesis of the results obtained. It also presents one method for testing in laboratory, to double check the correctness of the results of the real high voltage line parameter measurements, because they seem to be abnormal, different from those previously considered as normal. The results of the measured parameters obtained in the laboratory model confirm the results obtained on the real high voltage lines. Finally, I present the theoretically explanation of this results.

DETECTION OF Ne VIII IN AN INTERVENING MULTIPHASE ABSORPTION SYSTEM TOWARD 3C 263

We report the detection of Ne viii in an intervening multiphase absorption line system at z = 0.32566 in the Far Ultraviolet Spectroscopic Explorer spectrum of the quasar 3C 263 (zem = 0.646). The Ne viii λ770 Å detection has a 3.9σ significance. At the same velocity, we also find absorption lines from C iv, O iii, O iv, and N iv. The line parameter measurements yield log [N(Ne viii) cm−2] = 13.98+0.10−0.13 and b = 49.8 ± 5.5 km s−1. We find that the ionization mechanism in the gas phase giving rise to the Ne viii absorption is inconsistent with photoionization. The absorber has a multiphase structure, with the intermediate ions produced in cool photoionized gas and the Ne viii most likely in a warm collisionally ionized medium in the temperature range (0.5–1.0) × 106 K. This is the second ever detection of an intervening Ne viii absorption system. Its properties resemble the previous Ne viii absorber reported by Savage and colleagues. Direct observations of H i and O vi are needed to better constrain the physical conditions in the collisionally ionized gas phase of this absorber.

Spectroscopic line parameters of water vapor for rotation-vibration transitions near7180 cm−1

We present low uncertainty measurements of line parameters for 15 rotation-vibration transitions of water vapor in the wave number range of $7170.27--7183.02\text{ }{\text{cm}}^{\ensuremath{-}1}$. These experiments incorporated frequency-stabilized cavity ring-down spectroscopy and a primary standard humidity generator which produced a stable and accurately known amount of water vapor in a nitrogen carrier gas stream. Intensities and line shape factors were derived by fitting high-resolution spectra to spectral models that account for collisional narrowing and speed-dependent broadening and shifting effects. For most transitions reported here, we estimate the relative combined standard uncertainty of the line intensities to be $<0.4%$, of which approximately one half this value we ascribe to limited knowledge of the line shape. Our measured intensities and broadening parameters are compared to experimental and theoretical literature values. Agreement between our experimental intensity measurements and those derived by recent ab initio calculations of the dipole moment surface of water vapor is within 1.5%.

The spectrum of acetylene in the 5-μm region from new line-parameter measurements

Abstract Using Fourier Transform spectra (unapodized FWHM: 0.002 cm −1 ) of acetylene 12C2H2, absolute line positions have been obtained in the 5-μm region for about 490 lines belonging to 15 hot bands arising from the v4=1 or v5=1 lower vibrational level, improving the data available in this spectral region. Absolute line intensities have been measured for about 410 lines, from which vibrational transition dipole moments squared could be determined, as well as empirical Herman-Wallis coefficients when it was possible. The self-broadening coefficients of more than 370 lines have been measured at room temperature, showing that no vibrational dependence exists for the bands of acetylene already studied, and allowing a significant determination of their rotational dependence. Furthermore, about 120 measured values of self-shifting coefficients are tentatively proposed. Combining results published for other bands, and using the smoothed line-parameter values obtained in this work, a HITRAN-format line list of the acetylene molecule has been set up in this spectral region.

Line parameter measurements of trace gases in the near infrared region

The absorption spectra of CO 2, CO, and N 2O in the near infrared region were measured with a high-resolution Fourier transform spectrometer to examine the uncertainties of the line parameters of spectroscopic databases. The line strengths and half-widths of these molecules were determined by a nonlinear least squares technique. We compared our results with the values compiled in the HITRAN databases. Large differences between the measured line strengths and the compiled ones in the HITRAN databases were found for the weak bands of each molecule. The Herman-Wallis coefficient was determined for the first overtone band of CO. Self-broadened half-widths of CO 2 and N 2O agreed with the HITRAN96 values; while self-broadened half-widths of CO were different from the HITRAN96 values. N 2 − and O 2 − -broadened half-widths of CO were very close to the values previously reported by others.

Long-term spectroscopy of η Carinae

Quantitative measurements of line parameters in the spectrum of η Carinae are presented for both the broad and narrow line components. A total of 655 spectral features were measured in the spectral range 3850 A to 11000 A, giving a comprehensive view of the behavior of atomic transitions ranging from a few to tens of electron volts. The spectrum on the phase of maximum intensity in the high excitation lines (1995) is compared with that on minimum intensity (June 1992), showing that at this phase the high excitation lines disappear but the broad components of low excitation lines strengthens. We reject a number of previous line identifications and propose several new ones, including FeII, [FeII], [FeIII], [NII], and the near-infrared CaII triplet. Some lines commonly used to diagnose density, temperature, chemical composition, and reddening were found to be blended, urging a revision of the results based on previous data. The existence of double-peaked lines, suggested in previous papers, is ruled out. In the case of hydrogen lines, the apparent double-peaks are shown to be real absorption components. The velocity field in the inner 2 around the central star shows additional components previously unknown. The phases of high and low excitation in η Carinae are discussed in light of a recently proposed binary system. We suggest a temperature T ~ 16000 K for the primary star, what indicates that it is close to the beginning of the core helium-burning evolutionary stage.

Fourier spectroscopy with a very long optical path length

A description is reported of the 22 m maximum path difference Fourier transform spectrometer built in the laboratory in order to obtain Doppler limited spectra of heavy molecules in the infrared region. Main limitations in resolution and spectral line parameter measurements are given for this spectrometer at the present time of its evolution.

Phase errors on interferograms: influence on the determination of positions, intensities, and widths of lines in the infrared

The effect of a phase error on line parameter measurements by using Fourier-transform spectra is studied, showing that, to obtain accurate results without modifying the interferogram, it is necessary to adjust a computed spectrum to an experimental spectrum in which the phase error is taken into account.

Digital signal processing algorithms for power and line parameter measurements with low sensitivity to frequency change

A novel approach to definition of digital signal processing algorithms using bilinear form representation is introduced. The new algorithms are used to calculate power system power and line parameter values based on the current and voltage samples. The bilinear form approach provides a convenient methodology for optimal design of digital signal processing algorithms. This feature is utilized to design digital algorithms for power and line parameter measurements with low sensitivity to system frequency change. Several different algorithms are defined and their performance is investigated by testing their sensitivity to system frequency change. Various sampling rates and different data windows are utilized to define several test cases. >

Line parameter measurements and calculations of CO broadened by H 2O and CO 2 at elevated temperatures

Measurements of collisional broadening of four fundamental CO lines in atmospheres of CO 2 and H 2O at 300–600 K were made. The Voigt line-shape model was fitted parametrically to the absorption spectra line-shapes. The results are compared with other experimental studies and with theoretical calculations for CO 2 broadening. Absorption spectra of the exhaust gases of a flat flame were recorded and analyzed to yield CO concentration, temperature, and line half-widths. The flame spectra half-widths were compared with extrapolations of lower temperature data using the simple power law approximation γ(T)=γ(T 0) ( T 0 T ) n . The utility of this approximation in the development of combustion diagnostic techniques is discussed.

Line parameter measurements and calculations of CO broadened by nitrogen at elevated temperatures

Measurements of the line strengths and collisional broadening widths of CO in a N 2 atmosphere were made from 300 to 600 K. The lines studied were the P(2), P(3), P(7), P(12), P(18), and P(22) lines of the fundamental band at 2100 cm −1. The absorption spectra were parametrically fit to a Voigt lineshape model. The band strength was determined to be 250±8 cm −2atm −1. The broadening results are compared to Anderson-Tsao-Curnutte calculations and to other experimental studies. The possibility of using an equation of the form γ(T)=γ(T 0( T 0 T ) n to extrapolate the temperature dependence of the half-widths to flame temperatures is discussed.