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Your search keyword '"Mirzaie, Mohammad"' showing total 273 results
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273 results on '"Mirzaie, Mohammad"'

56. Designation of an Indicator for flashover prediction of porcelain and glass insulators based on experimental tests

Author

Mousalreza Faramarzi Palangar and Mirzaie, Mohammad

Subjects
lcsh:Production of electric energy or power. Powerplants. Central stations, Leakage current, lcsh:TK1001-1841, Harmonic, lcsh:Electrical engineering. Electronics. Nuclear engineering, Flashover, Insulators, Pollution, lcsh:TK1-9971
Abstract

Flashover of polluted insulators in contaminated areas is one of the most important factors influencing the operation of transmission and distribution lines and finally line outages. Therefore, it is essential to prevent and detect flashover in the insulators. Hence, utilizing the insulator status monitoring systems and predicting their functions have absorbed a lot of attention over the recent years. In this paper, a new method is proposed for flashover prediction in porcelain and glass insulators. In this regard, a variety of experiments has been conducted on different types of insulators under different environmental conditions and analysis of their leakage current harmonics have been investigated. Fast Fourier Transform (FFT) analysis applied to the saved leakage current waveforms shows a strong correlation between the ratio of the third to fifth harmonic amplitudes by regarding the occurrence of critical conditions and degree of insulator ageing. Then, the third to fifth harmonic ratio of the leakage current (R3/5) has been proposed as an indicator of critical conditions in porcelain and glass insulators. The results of these experiments show that the mentioned harmonic ratio has a definite and constant procedure against the changes in the type of pollution and humidity rate. The results of experiments have indicated that increasing the index R3/5 to more than one represents a critical condition in the insulators and estimates a high probability of flashover. Also in whole the tests, value of the total harmonic distortion (THD) and flashover voltage are measured.

Published
2015

64. Stable laser-plasma accelerators at low densities.

Author

Song Li, Hafz, Nasr A. M., Mirzaie, Mohammad, Xulei Ge, Sokollik, Thomas, Min Chen, Zhengming Sheng, and Jie Zhang

Subjects
LASER-plasma interactions, PLASMA accelerators, FILAMENTATION instability, ELECTRON beams, PLASMA density
Abstract

We report stable laser wakefield acceleration using 17-50 TW laser pulses interacting with 4mmlong helium gas jet. The initial laser spot size was relatively large (28 lm) and the plasma densities were 0.48-2.0×1019cm-3. High-quality 100-MeV electron beams were generated at the plasma density of 7.5×1018cm-3, at which the beam parameters (pointing angle, energy spectrum, charge, and divergence angle) were measured and stabilized. At higher densities, filamentation instability of the laser-plasma interaction was observed and it has led to multiple wakefield accelerated electron beams. The experimental results are supported by 2D particle-in-cell simulations. The achievement presented here is an important step toward the use of laser-driven accelerators in real applications. [ABSTRACT FROM AUTHOR]

Published
2014
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96. Insulation Condition Assessment of Power Transformers Using Accelerated Ageing Tests

Author

MIRZAIE, Mohammad, GHOLAMI, Ahmad, and TAYEBI, Hamid Reza

Subjects
General Computer Science, Transformer,insulation assessment,monitoring,polarization,recovery voltage, Electrical and Electronic Engineering
Abstract

Thermal stress due to losses and environment temperature causes degradation to paper/oil insulation systems in transformers, even at operating temperature. Experience indicates that thermal ageing of oil and paper in power transformers leads to the change of some insulation characteristics. In this paper, insulating papers immersed in oil have been acceleratory aged at 140, 150, and 160 °C under laboratory conditions. Some of the oil properties, such as water content, breakdown voltage, acidity, together with the aged insulating paper properties such as electric strength, dielectric dissipation factor and tensile strength were measured and analyzed. Also, insulation system conditions under thermal stress have been evaluated by electrical/distinctive techniques like recovery voltage, polarization and depolarization currents. Correlations between these parameters have been investigated. Finally, paper tensile strength has been used as a criterion to estimation of insulating paper life time.

Published
2009

97. Calculation of losses and ampacity derating in medium-voltage cables under harmonic load currents using finite element method.

Author

Rasoulpoor, Masoumeh, Mirzaie, Mohammad, and Mirimani, Seyyed Mehdi

Subjects
*ELECTRIC loss in electric power systems, *POWERLINE ampacity, *FINITE element method, *ELECTRIC cables, *HARMONIC analysis (Mathematics)
Abstract

This paper investigates the influence of metallic sheaths on alternating current (AC) losses and ampacity of power cables. The AC losses are expressed as AC/direct current (DC) resistance in power cables, which is the main factor in loss computations. With regard to the importance of harmonic contents of the currents, a comprehensive study is performed on AC/DC resistance of medium-voltage cables in the presence of harmonics. Different harmonic frequencies include triple and nontriple orders are considered. A derating factor is proposed on the basis of cable constructions. Two types of sheathed and unsheathed medium-voltage power cables are considered. Also for metallic sheathed cables, 2 types of sheath grounding are investigated. It is shown that single-point bonding and both-ends bonding of sheaths have different effects on cable ampacity in harmonic frequencies. Moreover, different conductor cross sections and distances between cables are considered, and their effects on AC/DC resistance and ampacity derating are assessed. It is shown that these factors have important effects on AC/DC resistance and thus power cable losses. Furthermore, all cases are investigated in both flat and trefoil formations that are the most popular formations in power cables. To achieve precise results, we performed this study on the basis of finite element simulation, which is an exact way to cable losses computations in each configuration. [ABSTRACT FROM AUTHOR]

Published
2017
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