Traveling Wave Velocity Research Articles

Novel traveling wave fault location method for HVDC transmission line based on wavefront frequency

The key of traveling wave (TW) fault location (FL) method is the calculation of TW velocity and the calibration of TW wave head. In order to achieve high-precision FL, detailed transmission line (TL) parameters are needed to accurately calculate the TW velocity. In view of the problem that the existing high-precision TWFL methods are highly dependent on the calculation of TW velocity, the paper contributes to following aspects: (i) the mapping relationship between wavefront frequency and fault distance/fault pole is constructed; (ii) a neural network model suitable for FL and fault pole identification is designed, which is optimized by Particle Swarm Optimization (PSO) algorithm and Levenberg–Marquardt (L-M) algorithm; (iii) a complete FL scheme is proposed. In order to verify the FL accuracy of proposed method, an ±800 kV bipolar high-voltage direct-current (HVDC) transmission system model is constructed using PSCAD/EMTDC. According to the simulation results, the errors of FL is less than 0.2 km and the accuracy of fault pole identification is 100%. For the problems of fault type, fault resistance and noise, the proposed method shows high robustness.

Exploring changes in building strength using seismic wave deconvolution

In order to avoid the casualties caused by damaged buildings during strong earthquakes, it’s important and essential to understand the seismic design specifications of buildings. The motion of a building depends on the interferometry of building and ground motion, the coupling between building and ground, and the mechanical properties of the building. We applied deconvolution technique to the motion recorded to separate the building response and calculated the structural parameters (including traveling wave velocity, resonant frequency and attenuation parameter). Therefore, we can check medium’s state by tracking these parameters to avoid damaged building collapse in the next mega-earthquake. We deployed a seismograph array in the building to record the earthquakes and few months of ambient noise data. In addition, we divided the structure into lower and higher floors to calculate the layering velocity. We found that the wave velocities of the lower and higher floors are significantly different but the former exhibit stable variation. For the monitoring phase, we tried different stacking time-lengths and calculated the related traveling wave velocities which are similar to the analysis in earthquakes. From the above results, we concluded that the physical parameters of the building can monitor the healthy condition of structure. Finally, we hope these results would be helpful to build a long-term monitoring of building's healthy status and the assessment of seismic hazard.

Characterization of relativistic electron bunch duration and traveling wave structure phase velocity based on momentum spectra measurements

The Accelerator Research Experiment at Sinbad (ARES) linac at DESY aims to generate and characterize ultrashort electron bunches (fs to sub-fs duration) with high momentum and arrival time stability for the purpose of applications related to accelerator research and development, e.g., development of advanced and compact diagnostics and accelerating structures, test of new accelerator components, medical applications studies, machine learning, etc. During its commissioning phase, the bunch duration characterization of the electron bunches generated at ARES has been performed with an rf-phasing technique relying on momentum spectra measurements, using only common accelerator elements (rf accelerating structures and magnetic spectrometers). The sensitivity of the method allowed highlighting different response times for Mo and Cs2Te cathodes. The measured electron bunch duration in a wide range of machine parameters shows excellent agreement overall with the simulation predictions, thus demonstrating a very good understanding of the ARES operation on the bunch duration aspect. The importance of a precise experimental determination of the phase velocity of the first traveling wave accelerating structure after the electron source, for which we propose a simple new beam-based method precise down to a variation of one part per ten thousand respective to the speed of light in vacuum, is emphasized for this purpose. A minimum bunch duration of 20 fs rms, resolution-limited by the space charge forces, is reported. This is, to the best of our knowledge, around 4 times shorter than what has been previously experimentally demonstrated based on rf-phasing techniques with a single rf structure. The present study constitutes a strong basis for future time characterization down to the sub-fs level at ARES, using dedicated X-band transverse deflecting structures. Published by the American Physical Society 2024

A Flexible DC Ranging Scheme Based on Variational Mode Decomposition and Teager Energy Operator

In this paper, a new Cable fault location scheme is proposed for the existing flexible DC Cable fault location methods, in which the fault signal is mixed with noise and the traveling wave speed is affected by line parameters. This scheme is based on the propagation characteristics of fault line mode voltage traveling waves in flexible DC transmission. Firstly, the fault voltage is effectively decomposed using Variational Mode Decomposition (VMD). Then, the decomposed intrinsic mode functions (IMF) are reconstructed to obtain the high-frequency components of the recorded fault information. Finally, the traveling wave head is calibrated using the Teager Energy Operator (TEO). A dual terminal ranging algorithm that is not affected by wave velocity has been proposed, which can effectively avoid the impact of fault traveling wave velocity uncertainty on the ranging results. A dual ended flexible DC power grid model was built in PSCAD/EMTDC, and a large number of simulation results show that the algorithm proposed in this paper can accurately calibrate the fault traveling wave head, has little interference from transition resistance, strong noise resistance, and can obtain high-precision fault location results in different fault locations.

Fault Location Scheme for Multi-Terminal Transmission Line Based on Frequency-Dependent Traveling Wave Velocity and Distance Matrix

Fault Location Scheme for Multi-Terminal Transmission Line Based on Frequency-Dependent Traveling Wave Velocity and Distance Matrix

A Fault Location Method for Medium Voltage Distribution Network Based on Ground Fault Transfer Device

The arc suppression device based on ground fault transfer (GFT) has been preliminarily applied in the medium voltage distribution network (MVDN). An accurate travelling wave (TW) fault location method is proposed to extend the use of the ground fault transfer device. D-PMU is used as a travelling wave detection tool to record the transient voltage travelling waves of fault grounding and bus active grounding during arc suppression. Then, the faulty section is identified through the time difference of travelling wave arrival at the upstream and downstream measurement points. On this basis, the fault location equations of the arrival time and distance of the upstream travelling wave are established, and an accurate fault location method based on the arrival time difference of the travelling wave is proposed. The simulation model is established by PSCAD/EMTDC, and the results show that the method has high location accuracy, and the absolute error is less than 30 m. It is not affected by the TW velocity, the fault conditions, or the distributed power sources.

Heat transfer modification in an unsteady laminar boundary layer subject to free-stream traveling waves

A laminar, thermal boundary layer was forced computationally by free-stream, traveling-wave velocity fluctuations and the effects on the wall heat flux and skin friction were measured as a function of the phase speed of the disturbances and the streamwise location along the developing flow. The heat flux modification due to the flow forcing was significantly higher than the corresponding skin friction enhancement, and the dependence of these two transport properties on the phase speed was qualitatively different. The skin friction modification exhibited a maximum at an optimal phase speed, which was explained in terms of the overlap of two distinct viscous layers within the boundary layer. The heat flux modification did not exhibit this maximum, although evidence was found to suggest such a maximum may occur with sufficient boundary layer development. Because the magnitude of the wall heat-flux modification scales quadratically with wave amplitude, traveling wave disturbances pose significant challenges for thermal transport measurements in periodically perturbed environments, like turbomachinery, but also new opportunities for the control of heat transfer.

Traveling wave solutions to the inclined or periodic free boundary incompressible Navier-Stokes equations

This paper concerns the construction of traveling wave solutions to the free boundary incompressible Navier-Stokes system. We study a single layer of viscous fluid in a strip-like domain that is bounded below by a flat rigid surface and above by a moving surface. The fluid is acted upon by a bulk force and a surface stress that are stationary in a coordinate system moving parallel to the fluid bottom. We also assume that the fluid is subject to a uniform gravitational force that can be resolved into a sum of a vertical component and a component lying in the direction of the traveling wave velocity. This configuration arises, for instance, in the modeling of fluid flow down an inclined plane. We also study the effect of periodicity by allowing the fluid cross section to be periodic in various directions. The horizontal component of the gravitational field gives rise to stationary solutions that are pure shear flows, and we construct our solutions as perturbations of these by means of an implicit function argument. An essential component of our analysis is the development of some new functional analytic properties of a scale of anisotropic Sobolev spaces, including that these spaces are an algebra in the supercritical regime, which may be of independent interest.

Study of Vortex-Induced Vibration of a Pipe-in-Pipe System by Using a Wake Oscillator Model

A pipe-in-pipe (PIP) system is an important engineering structure in the petroleum industry. Under the excitation of ocean fluids, the PIP system produces vortex-induced vibration (VIV), which can affect the oil recovery efficiency of large offshore drilling platforms and cause various engineering accidents. In this work, a fluid–structure coupled vibration model of the PIP system excited by a vortex-induced force is established based on an Euler–Bernoulli double-beam model and a wake oscillator model. The harmonic balance method is used to solve the coupled vibration model. Influences of the connection layer stiffness, tension, mass ratio, phase angle, and frequency ratio on displacements of the PIP system are studied. It is shown from numerical results that displacements of inner and outer pipes increase with the slenderness ratio. Displacements of inner and outer pipes decrease with the connection layer stiffness, but the frequency ratio and traveling wave velocity increase with it. In addition, the frequency ratio of the PIP system exhibits a multivalued characteristic, which is the characteristic of a nonlinear system. A small stiffness of the connection layer can induce unstable vibrations. Displacements of inner and outer pipes decrease with the tension, but the frequency ratio increases with it. The collision time of the inner and outer pipes gradually increases with the tension. The pipe displacements decrease with the mass ratio.

Emergence of traveling waves and their stability in a free boundary model of cell motility

We consider a 2D free boundary model of cell motility, inspired by the 1D contraction-driven cell motility model due to P. Recho, T. Putelat, and L. Truskinovsky [Phys. Rev. Lett. 111 (2013), p. 108102]. The key ingredients of the model are the Darcy law for overdamped motion of the acto-myosin network, coupled with the advection-diffusion equation for myosin density. These equations are supplemented with the Young-Laplace equation for the pressure and no-flux condition for the myosin density on the boundary, while evolution of the boundary is subject to the acto-myosin flow at the edge. The focus of the work is on stability analysis of stationary solutions and translationally moving traveling wave solutions. We study stability of radially symmetric stationary solutions and show that at some critical radius a pitchfork bifurcation occurs, resulting in emergence of a family of traveling wave solutions. We perform linear stability analysis of these latter solutions with small velocities and reveal the type of bifurcation (sub- or supercritical). The main result of this work is an explicit asymptotic formula for the stability determining eigenvalue in the limit of small traveling wave velocities.

Modeling Spatial Waves of Wolbachia Invasion for Controlling Mosquito-Borne Diseases

Wolbachia is a natural bacterium that can infect mosquitoes and reduce their ability to transmit mosquito-borne diseases, such as dengue fever, Zika, and chikungunya. Field trials and modeling studies have shown that the fraction of infection among the mosquitoes must exceed a threshold level for the infection to persist. To capture this threshold, it is critical to consider the spatial heterogeneity in the distributions of the infected and uninfected mosquitoes created by a local release of the infected mosquitoes. We develop and analyze PDE models to study the invasion dynamics of Wolbachia infection among mosquitoes in the field. Our reaction-diffusion-type models account for the complex vertical transmission and the spatial mosquito dispersion. We characterize the threshold for a successful invasion with a bubble-shaped distribution, called the “critical bubble.” The critical bubble is optimal in its release size compared to other spatial profiles in a one-dimensional landscape. The fraction of infection near the release center is higher than the threshold level for the corresponding homogeneously mixing ODE models. We show that the proposed spatial models give rise to the traveling waves of Wolbachia infection when above the threshold. We quantify how the threshold condition and traveling-wave velocity depend on the diffusion coefficients and other model parameters. Numerical studies for different scenarios are presented to inform the design of release strategies.

Multiperiodic and chaotic wave phenomena of collective ion dynamics under KP-type equation in a magnetised nonextensive plasma

Dynamical features of small-amplitude ion-acoustic waves are investigated under KP-type equation in a magnetized electron-ion plasma, where electrons follow q-nonextensive distribution. To carry out this investigation, a four dimensional conservative dynamical system is proposed from this plasma model. By changing values of travelling wave velocity, ratio between ion gyro frequency and ion plasma frequency and q-nonextensive parameter, the system produces different dynamical features, such as periodic, multi-periodic, quasiperiodic, and chaotic ion-acoustic wave phenomena. It is observed that ratio between ion gyro frequency and ion plasma frequency plays the key role in the existence of ion-acoustic chaotic wave phenomenon. Also, existence of higher order periodic trajectories is seen to indicate chaotic phenomenon.

Traveling wave velocity independent fault location scheme with adaptive mathematical filters for distribution network

In this paper, a novel traveling wave fault location scheme suitable for multi-branch distribution network is proposed. First, to overcome the negative impact of noise signals, a method based on multiscale mathematical morphology is designed to extract the arrival time of fault-generated traveling waves, with the structure elements adaptively adjusted according to the characteristic of input signals. Then, two proper criteria derived from multi-end traveling wave method are used to identify the faulty line section and filter the valid time recorded by traveling wave detectors, respectively. Finally, a velocity-independent formula is presented to achieve the accurate fault location. Extensive simulation tests are carried out to evaluate the feasibility of the proposed scheme, and the simulation results verified that it is independent of the fault location, inception angle, impedance and noise interference.

A novel fault location method for hybrid lines based on traveling wave

In this paper, a novel fault traveling wave-based location method for hybrid lines is proposed. According to the refraction characteristics of fault traveling wave (TW) at junction nodes, the node ratio coefficient value Q is defined based on the amplitude of traveling wave. Then, by comparing the Q values of junction nodes and fault points, a fault section identification principle is proposed to determine the fault line section for hybrid lines. After identification of fault line section, a double-ended fault location method is revised via adding the location compensation factors to mitigate the effect of traveling wave velocity changes on fault location for multi-section hybrid lines. Additionally, considering the detection problems of arrival time for TW signals, the extreme-point symmetric mode decomposition (ESMD) method and Teager energy operator (TEO) are proposed. The ESMD method is applied to decompose the sampled fault traveling wave signals into several intrinsic modes to filter out the fundamental frequency and low frequency signals. The TEO is employed to track the characteristics of TW signals. Effectiveness of the proposed method is validated in PSCAD. Results show that the ESMD-TEO can detect TW signals effectively, and the proposed fault location method can determine the fault line section and locate fault positions correctly.

Multiple sawtooth-shape current reversals of traveling wave system

In this paper, we investigate current reversal (CR) of overdamped traveling wave system subjected to an symmetric periodic driving. Numerical results shown that current takes the form of sawtooth-shape, and its direction can reverse more than ten times with traveling wave velocity, called multiple sawtooth-shape CR here. In virtue of transformation of reference frame, we reveal that occurrence of the sawtooth-shape CR comes from step amplitudes induced by the periodic driving in the new reference frame, and reversal time of current depends on the driving and the spatial potential. Moreover, direction of the current changes with the increment of noise intensity in the rocking system, i.e., noise-induced CR, which has not been reported in previous works on stochastic traveling system, and the intrinsic physical mechanisms responsible for the CR is analyzed in detail.

Modeling of nonlinear ion-acoustic solitary, snoidal and superperiodic wave phenomena due to ionospheric escape of Venus

Solar wind induces the escape of ions from the ionospheric shell of an unmagnetized planet, Venus. To analyze the dynamics of ions due to the escape process, the modeling of ion-acoustic waves (IAWs) is scrutinized for an interaction between an upper ionospheric plasma of Venus constituting mobile electrons with two kinds of positive ions, viz, H+ and O+ and the solar-wind which is composed of highly energized electrons and protons. The Sagdeev pseudopotential is examined for wave breaking phenomena. Employing the concept of phase plane analysis, the formulated autonomous dynamical systems are examined for all feasible nonlinear and supernonlinear periodic waves. To support the existence of nonlinear and supernonlinear waves, the graph of the total energy function is plotted in three-dimensional space. A typical set of Venusian plasma parameters are used to discuss the analytical solutions of the dynamical system by the method of Jacobi elliptic function. Effect of traveling wave velocity on the plot of the total energy function and the wave solutions are discussed.

An accurate fault location method for distribution network based on active transfer arc-suppression device

Active transfer arc-suppression device is a kind of arc suppression device which has been widely used in the distribution network. When a single-phase grounding fault occurs, the bus of faulty phase is actively grounded metallicity in the substation to limit the voltage of faulty phase, so as to realize arc extinction. In this paper, an accurate fault location method is proposed for the distribution network equipped with active transfer arc-suppression device. According to the variation characteristics of the fault traveling wave signals before and after arc-suppression device operation, the fault location formula based on the traveling wave velocity difference of different modes and the fault location formula based on the mutation of aerial-mode traveling wave are combined to obtain the final fault location method that is not affected by ground-mode wave velocity. The proposed method expands the function of active transfer arc-suppression device, makes it have additional fault location ability, and greatly improves the economy of the device. Simulation verifies that the proposed method is not affected by fault conditions, soil resistivity and extreme fault. The absolute error is within 50 m in all cases, which has high reliability.

Inner hair cell stereocilia displacement in response to focal stimulation of the basilar membrane in the ex vivo gerbil cochlea

The inner hair cells in the mammalian cochlea transduce mechanical signals to electrical signals that provide input to the auditory nerve. The spatial-temporal displacement of the inner hair cell stereocilia (IHCsc) relative to basilar membrane (BM) displacement is central to characterizing the transduction process. This study specifically focuses on measuring displacement of the stereocilia hair bundles in the radial dimensions where they are most sensitive. To simplify the mechanical response of the cochlear partition, a mechanical probe was used to drive the BM. Optical imaging was used to measure radial displacement of the inner hair cell stereocilia local to the probe in ex vivo gerbil cochleae. The mechanical probe displaced the BM in the transverse direction using sinusoidal stimuli with frequencies ranging from 10 Hz to 42.5 kHz. IHCsc displacement measurements were made in the radial dimension as a function of their longitudinal location along the length of the BM. The results were used to quantify the frequency response, longitudinal space coupling, traveling wave velocity, and wavelength of the radial displacement of the stereocilia.The measurements were centered at two best frequency locations along the BM: Proximal to the round window (first turn), and in the second turn. At both locations, frequency tuning was seen that was consistent with published place maps. At both locations, traveling waves were observed simultaneously propagating basal and apical from the probe. The velocity of the traveling waves at the center frequency (CF) of the location was higher in the first turn than in the second. As the stimulus frequency increased and approached CF for a location, the traveling wavelength decreased. Differential motion of the BM and IHCsc was observed in the second turn as the stimulus frequency increased toward CF. The longitudinal coupling measured in this study was longer than observed in previous studies. In summary the results suggest that the shape of the wave patterns present on the BM are not sufficient to characterize the displacement of the IHCsc.

Fault location of hybrid three-terminal HVDC transmission line based on improved LMD

To reduce the impact of traveling wave velocity, wave head recognition, and LMD (Local Mean Decomposition) end effect and mode mixing on location accuracy, this paper presents a fault location method based on improved LMD for hybrid three-terminal HVDC transmission lines, which is not affected by wave velocity. Firstly, the improved LMD is used to get the time when the fault traveling wave first arrives at the four measuring terminals. Then the fault branch is identified according to the ratio of the time of the fault traveling wave arriving at the measuring terminal. Finally, the equation is listed according to the principle of traveling wave location and the measurement equation which is not affected by the wave velocity is deduced. A hybrid three-terminal HVDC transmission system model is built by PSCAD to simulate various faults and output fault data under various fault conditions. MATLAB is used to process the fault data and verify the location algorithm. The simulation results show that the location method proposed in this paper is not affected by fault distances, fault types, infeed levels and transition resistances. In addition, it has higher accuracy than LMD based on CSI (Cubic Spline Interpolation) algorithm, wavelet packet location algorithm and double-ended location method of using wave velocity calculation.

Novel travelling wave fault location principle for VSC-HVDC transmission line

Currently, voltage source converter (VSC) based high voltage direct current (HVDC) technology is widely utilized in power transmission system. It has high transmission efficiency, no commutation failure issue and ability to supply power to passive system. In order to enhance the reliability of VSC-HVDC transmission system and accelerate the maintenance progress, travelling wave (TW) fault location principle is adopted to discriminate the exact location of transmission line (TL) fault, and its fault location accuracy is highly related to TW arrival time detection and TW propagation velocity. Therefore, aiming to enhance the fault location accuracy, the paper proposes a novel TW fault location principle for VSC-HVDC transmission line. Firstly, the detailed calculation method of propagation velocity of TW along HVDC-TL is described. Secondly, a novel TW fault location principle is proposed including TW arrival time detection method and TW’s accurate frequency calculation method. Eventually, based on PSCAD/EMTDC, a typical ±400kV VSC-HVDC simulation model is established to validate the robustness of novel TW fault location principle against fault type issue, fault resistance issue and fault location issue.