Traveling Wave Theory Research Articles

Use of time delays between modal components in wavelet based fault location

This paper presents an improved fault location method based on the traveling wave theory of the transmission lines. Fault transients recorded at one end of a transmission line are processed to determine the distance from the fault location. Wavelet transform is utilized for this purpose. The proposed method also takes advantage of the different travel times of the modal components in differentiating between close-in and remote end faults. The approach has the advantages of being independent of the fault impedance, mutual coupling effects and series compensation capacitors. The method's performance for typical faults is illustrated using transient simulations obtained by an electromagnetic transients program.

The phenomenon of hearing: an interdisciplinary discourse. I

For the last century hearing has been considered a purely passive process. G. S. Ohm's and H. v. Helmholtz's resonance theory of hearing was widely accepted until Wien's fundamental objection led to G. v. Békésy's and O. F. Ranke's travelling wave theory, the hydrodynamics of the inner ear that distributes the frequencies along the basilar membrane, which acts as the "first filter". Seebeck, Licklider, Schouten, and deBoer emphasized also the time domain and developed the concept of periodicity hearing and the "residue phenomenon". However, it was not until the concept of the "cochlear amplifier" and "active hearing" with energy generation during the transduction process within the ear itself was introduced that the "second filter" could be understood. Kemp's echo was the key to this revolutionary step in the theory of hearing.

Study of power coil resonance phenomena based on traveling wave theory

New measurement capabilities allow greater in-depth investigations of the propagation of guided electromagnetic waves inside a coil. Based on numerous measurements of the frequency-dependent conductance and susceptance of various arrangements of cylindrical and disc-type single-layer air-core coils, resonance phenomena of such arrangements, and the main influencing factors, are investigated. The results show dependencies which can be quantified by the application of the theory of traveling waves to the propagation of guided waves in coils. A single method, which is based on the interpretation of real physical phenomena, enables the prediction of the resonance frequencies of all orders. >

Time-domain analysis of lossy transmission lines with arbitrary terminal networks

A numerical method based on traveling wave theory is presented for the transient analysis of lossy transmission lines with arbitrary terminal networks. The method is well suited to computer programming. By introducing the imaginary transmission line, the network is portioned into two parts. An approach by the S-matrix and the z-transform is applied to the arbitrary terminal networks and time convolution is applied to the lossy transmission lines. The time domain S-matrix required for the convolution is obtained by the use of a fast inversion of a Laplace transform. A time-domain wave flow for the network is considered. The voltage waves at the lumped part are obtained by the S-z method, and the time-domain S-matrix is convolved with the voltage waves on the imaginary and lossy transmission lines to obtain a time-stepping solution. Three numerical examples are presented to illustrate the application of the method. >

Two classes of solutions of the fluid and gas mechanics equations and their connection to traveling wave theory

Two classes of solutions of the fluid and gas mechanics equations and their connection to traveling wave theory

Induction from underground power circuits into parallel communication services

The paper describes a powerful method for computing voltages induced into pilot/communication cables in the event of a sudden fault in a neighbouring underground power circuit. The model uses multiconductor travelling-wave theory and is able to compute transient as well as steady-state induction. Given results clarify the extent to which transient effects add to postfault steady-state induction. The various factors affecting the level of induction are investigated, leading to the proposal of a simple formula. This formula is accredited against the standard of the full model and appears to offer sound practical estimates.

Digital travelling-wave protection of transmission lines

Almost all the algorithms proposed so far for the digital protection of transmission lines are of the distance type and involve the extraction of the fundamental components from the complex post-fault waveforms through the use of filters, whereas those based on the travelling-wave theory need only a short data window and no filtering. This paper presents two new algorithms of the latter type along with the results of digital simulation tests which confirm their viability.

Unified panel flutter theory with viscous damping effects

The idea of a unified panel flutter theory, investigated previously by the author, is amplified to make the inclusion of damping effects possible. The paper attempts to study the combined effects of the aerodynamic and structural types of damping on the flutter boundaries for simply supported panels in high supersonic Mach number flows. Classical plate theory and two-dimensional first-order aerodynamics are used. A closed-form rather than modal approach is used in the solution of the partial differential equation in the analysis to avoid convergence problems. The standing and traveling wave theories of panel flutter are compared. The dual nature of damping (stabilizing and destabilizing) is exposed. While the trends are similar to those already established for isotropic panels, the variables compared are generically defined to account for both the isotropic as well as the orthotropic properties of the panels.

Digitalized control system with simultaneous data sampling and fault protection

A digitalized control system with simultaneous data sampling has been developed to provide protection and control for power systems. The system architecture is characterized by a measuring scheme of source data through a digital potential and current device, an automatically synchronized sampling scheme, and a multiple computer configuration. The system also embodies the d'Alembert-relay protection principle, the theoretical soundness of which is justified by the travelling-wave theory. The protective relay has been under field test at a 275 kV substation.

Auditory Nerve and Brain Stem Volume-Conducted Potentials Evoked by Pure-Tone Pips in the CBA/J Laboratory Mouse

The short latency (less then 10 ms) auditory nerve and brain stem evoked potentials of Jewett were examined in the inbred CBA/J laboratory mouse. Tone pips, at nine frequencies from 4 to 64 kHz, were used to determine auditory nerve evoked potential (P1) thresholds. Maximum sensitivity occurred at 32 kHz, and a second sensitive area was seen at 56 kHz. With the exception of 32 kHz, as stimulus frequencies were increased in octave intervals, the 90 dB P1 amplitude also increased. P1 latency decreased as the stimulus frequency was increased up to 32 kHz, but this trend reversed with further increases of frequency. However, the P1 amplitude-latency function produced a better agreement of latency and frequency with the travelling wave theory for amplitudes less than 1 micro V, while amplitudes from 2 to 8 micro V were independent of frequency. Latency and amplitude input-output functions for responses from the four auditory brain stem loci suggest that auditory information is differentially processed as a function of frequency at each level, This is especially true for the inferior colliculus, which is most sensitive to 8-KHz stimuli.

Fault protection based on travelling wave theory (part i‐theory)

Fault protection based on travelling wave theory (part i‐theory)

Fault protection based on traveling wave theory. Part 2: Feasibility study

Fault protection based on traveling wave theory. Part 2: Feasibility study

Boundary-damped panel vibrations

Boundary-layer noise generation has motivated a one-dimensional sinusoidal vibration study of a narrow flat aluminum panel. The understanding of the response of this continuous system to sinusoidal excitation yields practical information which directly relates to the random excitation of the same system. Partial coverage extensional damping layers bonded to the fixed end of the panel were investigated using traveling-wave theory, transmission-line theory, and experimental analysis. These techniques establish the useful concept of an “impedance panel,” analogous to the acoustical impedance tube, which can be used to determine the complex termination impedance of any type of attaching method used with a supporting structure, whether a damping treatment is applied or not. The boundary or termination-type damping is shown to be more effective than a total coverage extensional damping layer of equal mass. Termination damping layers which gradually introduce the damping to an incident bending wave were shown to be significantly more effective than abrupt-type flat slab damping layers of equal mass. [Part of first author's Ph.D. dissertation.]

Time domain radiation and scattering by thin wires

Direct time domain solutions for radiation from and scattering by thin conducting wires are considered. The problem is formulated in terms of two coupled integrodifferential equations derived from the retarded potentials, the continuity equation, and the boundary conditions for the wire. Solution of these equations is effected using the method of moments resulting in a set of simultaneous time iterative matrix equations. A time domain reciprocity theorem suitable for thin wire objects is also presented. The theorem demonstrates the relationship between reciprocity and the adjoint operator for the problem. Two moment solutions are presented for straight wires: (1) a point tested solution, and (2) a pulse tested solution. The radiation field is found by direct application of the reciprocity theorem. All solutions are presented as algorithms suitable for computation. The algorithms are time iterative by nature, and inexpensive in terms of computer time. Computed results are presented for the straight wire scatterer excited by a plane wave with unit step time dependence. The “end fire” effects predicted by traveling wave theory are observed in the scattered field results. The source of these effects is shown to be the end of the wire last intercepted by the incident field. Additional results are presented for the straight wire antenna excited by a unit step voltage applied at an arbitrary driving point. The computed driving point current is compared to the results derived for the case of an infinite wire antenna over the time interval that the comparison is valid.

The Effect Of Capacitors On The Short-Line Fault Component Of Transient Recovery Voltage

The use of a capacitor to modify the line-side component of transient recovery voltage following a short-line fault is investigated. A method is presented based on traveling wave theory to show the modifying influence of capacitance. Empirical data is included to show the effect of the capacitance on interrupting capability. The effects of size, location, and the possibility of using carrier components are discussed.

An explanation of the travelling wave theory of hearing.

In this paper the cochlea of the ear is considered as a transmission line. Calculations have been carried out on a line whose capacity varies in an exponential way with distance and which has negligible losses. These have shown that a sinusoidal excitation does not propagate beyond a certain point in the line. It is also shown in the paper that it is legitimate to consider the cochlea as a line of this type.

Motor Surge Protection: at the Bus or at the Motor?

This paper describes a fast easy method for determining expected surge voltage with the help of traveling-wave theory. The intent is to assist the Design Engineer in deciding what degree of surge protection should be provided and where to locate it.

Wave Amplification in a Plasma Stream in a Medium of High Refractive Index

The problem is considered of an unbounded plasma stream with speed U traversing an infinite, homogeneous medium which has a fixed refractive index of arbitrary (real) value μ. The nature of the associated characteristic electromagnetic waves is studied, with particular reference to the existence of amplifying waves. It is shown that there is amplification if, and only if, μ > 1; and that for a wave whose direction of propagation makes an angle α with the plasma stream, the amplification depends to some extent on whether U cos α is greater or less than c/μ, and is near optimum when U cos α = c/μ. The results of the analysis are related to the travelling-wave theory of the generation of very-low-frequency noise by fast charged particles streaming through the exosphere, and it is concluded that the mechanism in its simplest form cannot account for the arrival at the earth of discrete frequencies.

A New Approach to the Calculation or the Lightning Perrormance or Transmission Lines III-A Simplified Method: Stroke to Tower

1. Simplified methods of calculating the voltage across the insulator string are presented based on field-theory concepts for a stroke to the tower with zero towerfooting resistance. 2. The voltage across the insulator string is composed of two components: (a). that produced by the rent and the charge fed into the tower and ground wires, and (b). that produced by the charge above the tower. 3. To calculate the voltage produced by the current and charge fed into the tower and ground wires, conventional traveling-wave theory and methods can be used provided the proper value of surge impedances are used. 4. Equations, based on field theory, are presented to calculate the ground wire and tower surge impedances and the conductor-to-ground mutual impedances. 5. The development of travelingwave theory directly from field theory places traveling-wave theory on a more rigorous basis. 6. To calculate the voltage produced by the charge above the tower, approximate simplified equations are given for a given stroke mechanism. These can be modified for other assumptions. 7. From examples and calculations given in this paper it is possible to gain some insight on the effect of tower geometry, number of ground wires, and position of the conductor on the voltage across the insulator string. Voltages were calculateed across the top and bottom insulator strings of the single-groundwire AEP-OVEC 345-kv tower, across the top insulator string of the two-groundwire AEP-OVEC 345-kv tower, and across the insulator string on the PW&P 220-kv tower.

Far field scattering from bodies of revolution

By use of approximations based on physical reasoning radar cross-section results for bodies of revolution are found. In the Rayleigh region (wavelength large with respect to object dimensions) approximate solutions are found. Examples given include a finite cone, a lens, an elliptic ogive, a spindle and a finite cylinder. In the physical optics region (wavelength very small with respect to all radii of curvature) Kirchhoff theory and also geometric optics can be used. When the body dimensions are only moderately large with respect to the wavelength, Fock or Franz theory can be applied, and examples of the circular and elliptic cylinder are presented. In the region where some dimensions of the body are large with respect to the wavelength and other dimensions are small with respect to the wavelength, special techniques are used. One example, the finite cone, is solved by appropriate use of the wedge-like fields locally at the base. Another example is the use of traveling wave theory for obtaining approximate solutions for the prolate spheroid and the ogive. Other results are obtained for cones the base perimeter of which is of the order of a wavelength by using known results for rings of the same perimeter.