Search

An automatic detector device (ADD) has been designed and built for monitoring insulators state in overhead distribution lines. The prototyped device is suitable for measurement and analysis of the insulator leakage current (LC) on lines of distribution systems to diagnose insulator state. It operates based on two diagnostic indicators, third to fifth harmonic ratio (R3/5%) of the insulator's LC signal and cosine of phase angle difference (P.D%) between fundamental signals of the voltage and LC. Experimental data of the indicators in various conditions and various insulators are used to train a classifier for determining reference values of the indices for insulator state detection. The instrument has two physically separate parts: receiver and transmitter. They communicate via a radio communication channel which improves the effectiveness of incident management. The transmitter samples the LC signal of the target insulator using a ferrite core along with a series of active electronic filters. The sampled LC signal is then sent to the receiver. The transmitted LC signal is analyzed by the microprocessor embedded in receiver CPU. Indicators of the transmitted LC signal are calculated and compared with reference values extracted from the classifier. The receiver determines the insulator's state based on the comparison of the estimated and reference values of diagnostic indicators for the target insulator. The performance of the prototyped ADD was evaluated experimentally in the laboratory as well as on overhead distribution lines. These performance tests confirmed reliable performance of the ADD. [ABSTRACT FROM AUTHOR]

Laser wakefield acceleration (LWFA) is a plasma-based electron beam accelerator technology that can deliver electron beams with energies up to several GeVs, depending mainly on the power of the used laser system and the electron injection scheme. Here, we present the results from a GeV electron accelerator with a high reproducibility and a charge up to 30 pC using 110–120-TW laser pulses and by employing the well-established self-truncated ionization injection (STII) mechanism. These electron beams can be further used via bremsstrahlung in high-Z solid materials for the generation of gamma-rays and positron beams, therefore, composing a compact radiation source for various applications. Here, we use the Monte Carlo simulation code “Geant4” for studying the properties of those radiations. As expected, the characteristics of the generated gamma-rays and positron beams showed a strong dependence on the incident electron beam, target material, and thickness. The trend of positrons and gamma-rays energies and yield is shown for different high-Z to low-Z targets with the same areal mass density. Thicknesses of the target material in terms of its radiation length have been varied periodically in order to find the optimal thickness for obtaining the maximum energy and yield of the radiations. A trend can be seen in terms of energy spectra of the gamma-rays and positrons while increasing the thickness of the targets. The amount of radiation yields is also crucial to the choice of appropriate thickness of the target. In addition, this paper provides a brief description of the electrodynamics processes such as bremsstrahlung and electron–positron pair production initiated by LWFA electron beams. [ABSTRACT FROM AUTHOR]

In this paper, an improved method to diagnose the critical conditions in the porcelain and glass insulators has been proposed through investigating leakage current (LC) and applied voltage signals. Hence, Fast Fourier Transform (FFT) analysis has been used to calculate the phase angle values of the applied voltage and LC signals. Analyzing phase angle difference of LC and applied voltage waveforms demonstrate a strong correlation of the phase difference between the applied voltage and LC waveforms with the insulators conditions. So, the phase difference cosine (P.D%) has been offered as a diagnostic index of porcelain and glass insulators conditions. In this case, when the P.D% value is lower than 30%, the insulators are in clean and normal conditions. On the other hand, if the P.D% is more than 30%, the insulators are in extreme conditions. Moreover, by increasing %P.D value more than 85%, the probability of the flashover occurrence in porcelain and glass insulators will be very high. The obtained experimental results validate the veracity of considering P.D% as a criterion for prediction of flashover in porcelain and glass insulators. [ABSTRACT FROM PUBLISHER]

We report a laser wakefield acceleration of electron beams up to 130 MeV from laser-driven 4 mm long nitrogen gas jet. Using moderate laser intensity ( \sim 35\times 10^18~W\cdot cm^-2 ) and relatively low plasma densities ( 0.8\times 10^18~\mathrmcm^-3 -2.7\times 10^18~\mathrmcm^-3 ), we have achieved stable laser propagation and consequently stable acceleration of electron beams. We experimentally studied the dependence of the electron beam parameters on the laser beam energy. Evidence of the ionization-induced electron injection has been recognized from the characteristic long-tail beam energy spectrum, however, the majority of the electrons were contained in quasi-monoenergtic peaks. [ABSTRACT FROM PUBLISHER]