Partial discharges may occur in defective insulation systems of high voltage equipment, such as gas insulated substations and power transformers. These discharges generate electromagnetic waves that ...can be detected using ultrahigh frequency (UHF) sensors. UHF sensors must meet certain sensitivity criteria over a wide frequency range so as to be capable of detecting small discharges. Sensor frequency response is measured using a gigahertz transverse electromagnetic calibration system. Previous research has shown that finite-difference time-domain (FDTD) simulation of the calibration process can accurately model the response of the existing sensors. The work reported here demonstrates how a new sensor can be designed entirely using FDTD modeling. The proposed new partial discharge sensor has a physical construction that was selected to make it more robust, simple to manufacture, and convenient to install on metal-clad high-voltage apparatus. The internal structure of the UHF sensor was developed and optimized entirely within the FDTD software domain before the physical device was manufactured and tested. Simulated and experimental calibration results were found to be in agreement to within 10%. This finding validates the design methodology and optimization process. The approach described in this paper will help to streamline the design of UHF partial discharge sensors for specific applications in future.
Giga-Hertz Transverse Electromagnetic (GTEM) cell is a simpler and cheaper alternative to the full-scale anechoic chamber. It is an equipment of choice in a lot of partial discharge (PD) research, ...especially for antenna validation. According to a good practice the cell must be validated, or also known as calibrated, for its usability. The calibration term means validating the uniformity of electrical field produced at the point of measurement. This paper introduced a verification technique to be used to validate the integrity of input and response signals. This step is essential so that the reproducibility of the experiment is warranted and also to support the calibration analysis result. It was found that the input and response signals were reproducible and consistent. The calibration analysis on the existing bespoke GTEM showed that electric field uniformity at the prescribed area of testing complied with an established practice. Therefore, the GTEM cell can be used to conduct related experiment.
This paper aims to study a suitable permanent magnet linear generator (PMLG), designed to cater to the Malaysian wave condition. Most researchers focus their studies on locations with higher wave ...heights and longer wave periods, which is unsuitable for Malaysian wave conditions. The design of a 3-phase linear generator was simulated using Ansys software. Different dimensions for the winding, stator, and permanent magnet configuration were simulated to find suitable designs that could produce a higher output voltage. The result shows that the design with a higher number of coil turns can produce a higher output voltage. Moreover, the effective dimensions of the stator and permanent magnet also play a significant role in producing larger amounts of output voltage. The highest output voltage for the effective design is 11.57 V per phase with a wave velocity of 0.14 m/s.
Power Generation from Wave Energy using Floating Device Mohd Fadzil, N. A.; Ishak, A. M.; Abu Hasim, A. S. ...
2018 International Conference on Electrical Engineering and Computer Science (ICECOS),
2018-Oct.
Conference Proceeding
In Malaysia, there are a lot of islands that use diesel generators to generate electricity. This is because of expensive power connection from the grid system. However, when using the generators, it ...contributes to high pricing of diesel and difficult to distribute the supply to each island. Furthermore, the source is not sustainable and can affect environment due to carbon monoxide and carbon dioxide from the generators. Therefore, renewable energy sources have becomes an alternative solution for these problems. The advantages of using renewable energy are it is sustainable resources, produce clean energy, and low operating cost. One of the possible renewable energy sources is sea wave energy. There are few techniques to generate power from wave energy which are oscillating water column (OWC), tapered channel (TAPCHAN) and floating device. From this project, the technique of floating device (linear generator) was chosen because this technique is more affective and only requires small area of construction. SOLIDWORKS software was used to design the prototype for this project. From the result, the designed model can produce about 13mV. The effect of wave heights, number of turns, and diameter of coil wire were analyzed.
A direct-drive system with a permanent magnet linear generator has been an attractive solution for wave energy converter devices. Exploiting the reciprocating movement of wave motion has enabled the ...application of linear generators to wave energy converter devices. This paper presents the computational simulation of the Permanent Magnet Linear Generator design for a point absorber wave energy converter. The electromagnetic analysis was done using the Finite Element Analysis software, ANSYS. With this analysis, results on the flux distribution, air gap flux density and open-circuit results of the proposed design were gathered. A lab-scale device was constructed to validate a simple version of a single-phase linear generator design. A comparative study of both simulation and experimental results of the linear generator was carried out. Based on the results, the percentage error between simulation and experimental obtained was acceptable. To maximize power generation, an improved version of the linear generator based on an actual ocean profile was proposed.
Electron avalanches in liquid argon mixtures Kim, J.G.; Dardin, S.M.; Kadel, R.W. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2004, Letnik:
534, Številka:
3
Journal Article
Recenzirano
Odprti dostop
We have observed stable avalanche gain in liquid argon when mixed with small amounts of xenon (xe) in the high electric field (
>
7
MV/cm) near the point of a chemically etched needle in a ...point–plane geometry. We identify two gain mechanisms, one pressure dependent, and the other independent of the applied pressure. We conclude that the pressure-dependent signals are from avalanche gain in gas bubbles at the tip of the needle, while the pressure-independent pulses are from avalanche gain in liquid. We measure the decay time spectra of photons from both types of avalanches. The decay times from the pressure-dependent pulses decrease (increase) with the applied pressure (high voltage), while the decay times from the pressure-independent pulses are approximately independent of pressure or high voltage. For our operating conditions, the collected charge distribution from avalanches is similar for 60 or 122
keV photon sources. With krypton additives, instead of Xe, we measure behavior consistent with only the pressure-dependent pulses. Neon and TMS were also investigated as additives, and designs for practical detectors were tested.
Electron avalanching in liquid argon is being studied as a function of voltage, pressure, radiation intensity, and the concentrations of certain additives, especially xenon. The avalanches produced ...in an intense electric field at the tip of a tungsten needle are initiated by ionization from a movable americium (/sup 241/Am) gamma-ray source. Photons from xenon excimers are detected as photomultiplier signals in coincidence with the current pulse from the needle. In pure liquid argon, the avalanche behavior is erratic, but the addition of even a small amount of xenon (/spl les/100 ppm) stabilizes the performance. Similar attempts with neon (30%) as an additive to argon have been unsuccessful. Tests with higher energy gamma-rays (/sup 57/Co) yield spectra and other performance characteristics quite similar to those using the /sup 241/Am source. Two types of signal pulses are commonly observed: a set of pulses that are sensitive to ambient pressure and a set of somewhat smaller pulses that are not pressure dependent.
Previously, we showed how small admixtures of xenon (Xe) stabilize electron avalanches in liquid Argon (LAr). In the present work, we have measured the positive charge carrier mobility in LAr with ...small admixtures of Xe to be 6.4/spl times/10/sup -3/ cm/sup 2//Vs, in approximate agreement with the mobility measured in pure LAr and consistent with holes as charge carriers. We have measured the concentration of Xe actually dissolved in the liquid and compared the results with expectations based on the amount of Xe gas added to the LAr. We also have tested LAr doped with krypton to investigate the mechanism of avalanche stabilization.
The DIRC particle identification system for the BaBar experiment Aleksan, R.; Amerman, L.; Aston, D. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
02/2005, Letnik:
538, Številka:
1-3
Journal Article
Recenzirano
Odprti dostop
A new type of ring-imaging Cherenkov detector is being used for hadronic particle identification in the BABAR experiment at the SLAC B Factory (PEP-II). This detector is called DIRC, an acronym for ...Detection of Internally Reflected Cherenkov (Light). This paper will discuss the construction, operation and performance of the BABAR DIRC in detail.
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