Papers by Keyword: Traveling Wave

Abstract: Traveling wave in transit, wave head is easy to produce distortion and affected by environmental interference, so accurately measuring the head of traveling wave singularity occurrence time become extremely difficult. The key to improve the precision of traveling wave detection is to accurately capture the happening time of wave head of singular points. Recently, traveling wave singularity detection usually use wavelet, EMD-HHT transform technique, but both have mixing phenomenon, affecting the accuracy of detection. In this paper, we propose a new method that use Duffing chaotic oscillator to suppress traveling wave interference signal. By Matlab simulation and it is proved that this method can effectively suppress noise singular point. Meanwhile, we propose an anti-mixing EEMD-HHT wave head detection technology. Through simulation experiment and field test, it is proved that, compared with EMD, EEMD can more accurately identify the traveling wave arrival time, detection accuracy increasing by 1.52%.

Abstract: Piezoelectric actuators are widely used for the nano/micro positioning and adjustment systems. In the paper, the investigation on the oscillations of contacting surfaces of the piezoelectric thick-walled cylinder is presented. Piezoelectric cylinder is the main component of piezomechanical system named as piezo-screw and is used to turn the screw. This investigated piezomechanical system can be used for the precise positioning with a high resolution (less than 50 nanometers). Piezoelectric cylinder has radial polarization. Traveling-wave oscillations of the second circumferential modal shape (n = 2, m = 1) are excited. Three different electrode topologies are used to drive the screw. Electrodes are grouped into upper and low groups in both topology cases. Each group consists of six electrodes where positions of corresponding electrodes in upper and lower group are shifted by π/6. Numerical investigation of the traveling wave oscillation is performed and dependencies oscillation trajectories of contact surfaces on excitation schemes are determined when three different electrode topologies are used. Dependency of oscillations of contacting points upon length of the actuator is analyzed as well. Advantages and disadvantages of each excitation case are discussed.

Abstract: The conventional approaches to distribution network fault location has certain drawbacks in terms of complexity, especially the fault occurred in the branch lines. In this paper, a novel fault location method based on D-type traveling wave was proposed. This method choose the measurement point which the initial traveling waves first reached as the reference measurement point, and the distance between multiple failure points received a fault traveling wave signal to the reference measurement point was calculated. Then, the maximum distance between multiple failure points to the reference measurement point was selected as location of the final failure point. The simulation result with ATP simulation software and MATLAB software show that the proposed method can achieve fault location fast and accurately within a very short period. Compared with the existing algorithms, this method was consistent whether the fault occurred in the main line or branch lines, which improved the accuracy and reliability of the traveling wave fault location in distribution network.

Abstract: A new de-icing method is proposed based on the traveling wave piezoelectric theory, which is to remove residual ice on the fix points of the aircrafts. Testing equipment is designed as the following steps. Firstly, without piezoelectric ceramics, modal analysis of the testing skin which the dimension is 270×90×1.5 mm is completed to confirm the position of the piezoelectric ceramics. The piezoelectric ceramics are adhered to the testing skin with the maximum strain of the bending modes which the frequencies along X and Y direction are close to each other based on the above modal analysis. Then, the harmonic response analysis of the testing skin with ceramics is carried out to study the available excitation frequency in which the skin can travel looply. Finally, the equipments are fabricated to verify the numerical simulations. It is obtained that the excitation frequency to form the traveling wave is from 5099 to 5121 Hz. The input voltage passes 400 V can de-ice when the adhesive strength is set as 2 MPa in von Mises yield criterion. If the refrigerated ice is similar to the aerial ice, it is easily removed by the experimental equipments. However, it is required to further the research because this de-icing technique is still in its infancy.

Abstract: Distributed way of traveling-wave fault location algorithm is a new theory founded in recent years. By installing sensing points in distributed way, the accuracy of fault location result can be clearly improved comparing to traditional methods. First, PSCAD is used to simulate the transmission line model and measure the three-phase current data. Second, by using wavelet transformation and phase to-module transformation, these current data is mathematically processed and modulus maximum is achieved easily. Finally, time difference between the adjacent modulus maximum points is calculated and the location is figured out by using the module time-difference algorithm. The test result shows that the method above is valid and the relative error is rather small.

Abstract: Among the available fault location methods based on traveling waves, calibrations of wave velocity and wave arrival time are the two main problems. This paper proposes a new fault location method which combines the two problems mentioned above. In this method, the first wave and second wave obtained at one side and the first wave obtained at the other side is used to locate the fault point. And the Hilbert-Huang transform is used in the calibration of wave arrival time, making the method more accurate than using wavelet transform. This method has the following two advantages: At first, it dismisses the influence of wave velocity. In the second, it doesn’t need to distinguish the sources of the received waves. ATP-EMTP’s simulation results show that this method is available and the location precision is higher than traditional fault location methods.

Abstract: Double circuit transmission line is an important part of the power grid, which is vulnerable to lightning and may endanger the security and stability of the power grid. In order to design a sensor which can monitor the lightning traveling wave current on double circuit transmission line, simulations of lightning on the double circuit transmission line were conducted. The simulation result shows that besides high frequency components, the traveling wave contains a lot of low frequency components. Based on the equivalent model and the frequency response of the self-integrated Rogowski coil, it turns out that the widely used self-integrated Rogowski coil is not suitable for this application as the problem of low frequency distortion. In this paper, through theoretical analysis and simulations in Matlab, an improved Rogowski coil with analog integrator is proposed which can correct the low frequency distortion of the self-integrated Rogowski coil. All the simulations, experiments and operating data installed to a double circuit transmission line in China verify the validity of the high bandwidth Rogowski coil.

Abstract: Wavefront identification is important for traveling based fault location. In order to improve its reliability, a novel wavefront identification method based on Harris corner detector has been proposed in this paper. The principle of single-ended traveling wave fault location was briefly introduced at first, and the features of wavefronts generated by faults on transmission lines were analyzed. The arrival of traveling waves' wavefronts is considered as corner points in digital image of waveshape. The corner points can be extracted precisely by Harris corner detector, and both false corner points and non-fault caused disturbance can be eliminated according to the calculated distance between two neighbour corner points and the angle of the corner point. The proposed method is proved feasible and effective by digital simulated test.

Abstract: Taking Jiashao Bridge as the research subject, this paper established finite element model by ANSYS to study random seismic response of multi-tower cable-stayed bridge. The results show that the constraint relations between tower and girder influence internal force at bottom of towers deeply, and the force of each tower is different. The vertical displacements in the midspan of girder are varied in different constraint relation. In addition, the effect of traveling waves on this bridge under excitation was analyzed, the results show that traveling wave velocity has an important implication on the seismic response of multi-tower bridge, and there are some regular relations between the response of structure and high traveling wave velocities.

Abstract: Hydrostatic bearing is wildly utilized in many precision applications and positioning stages due to their ability to support designed load at zero relative speed between bearing and guide surfaces. However, in practice external pressurized source is necessary for realizing the hydrostatic bearing, which sometimes leads to difficulty in some medical and aero applications within tightly sealed container. In order to tackle this problem, an innovative principle bearing, which utilizes traveling waves, has been proposed by authors in previous researches. The proposed principle is ought to eliminate drawbacks of conventional hydrostatic bearing such as external pressure source, use of compressor, external pump and tubing system, while still achieving comparable static and dynamic capabilities. Based on the proposed principle, a prototype device of liquid bearing utilizing traveling waves was developed and analyzed by experiments in this present paper. Its floating and smooth motion is confirmed by experiments here.