Iranian Journal of Electrical and Electronic Engineering

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A new heterodyne nano-displacement with error reduction is presented. The main errors affecting the displacement accuracy of the nano-displacement measurement system including intermodulation distortion error, cross-talk error, cross-polarization error and phase detection error are calculated. In the designed system, a He-Ne laser having three-longitudinal-mode is considered as the stabilized source. The free spectral range of the 35cm laser cavity is about 435-MHz at 632.8-nm wavelength, which a secondary beat frequency equal to 300-kHz is produced by combining the reference and measurement beams. The resolution of the displacement measurement resulting from intermodulation distortion, cross-talk and cross-polarization errors is limited to 18-pm. Also, the phase detection uncertainty causes an error of only 5.9-pm in the displacement measurement. Furthermore, frequency-path models of two- and three-longitudinal-mode laser interferometers are modeled as the ac interference, ac reference, dc interference and optical power terms. A comparison study between two- and three-longitudinal-mode laser interferometers confirms that the performance of the designed system is considerably improved.

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Abstract: The application of electric field theory to widely different aspects of electrical insulation has led to more understanding the phenomena. Electric fields may be considered as the main reason for insulation failure. The purpose of this paper is to modify importance of analyzing electric field in insulation design. The SF6 circuit breaker is chosen as case study that encounters critical situations during its application. The other phenomena affects insulation is the presence of polar species in a non-polar molecular material locally modifies the polarization energy, thus creating local states (traps) on neighboring molecules. Results of calculations carried out for arrays of spatially connected dipoles indicating that local states of a considerable density may be created, modifying the densityof- states function, and therefore influencing the effective mobility of charge carriers. The main result of polarization during application in circuit breaker is loss of life. In this paper the reduction of negative effects of electric field and polarization by choosing a suitable insulation structure in a 33 kV SF6 circuit breaker according to calculation in critical areas is investigated that can also be studied in other types of circuit breakers.

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Electromagnetic waves, with their unique properties, offer promising solutions to environmental challenges. This paper explores the utilization of electromagnetic scattering by droplets for cloud fertilization purposes. Specifically, a linearly polarized plane wave is deployed to stimulate a heterogeneous cloud medium composed of spherical droplets with varying size parameters. Through the application of Generalized Mie Theory (GMT) and Discrete Dipole Approximation (DDA) at a frequency of 28 GHz, multiple scattering phenomena and local electric fields are meticulously computed. Various scenarios of scattering, encompassing droplet diameters ranging from 500 µm to 700 µm and diverse volume fractions, are meticulously examined. Employing DDA and dyadic calculations, the exerted forces on individual spherical droplets are rigorously evaluated, with precise determination of force direction and components. The simulations robustly affirm the viability of droplet manipulation via plane wave excitation, thereby enhancing the likelihood of droplet collision and consequent cloud fertilization, ultimately leading to precipitation. Furthermore, the parameters of the incident wave can be deliberately adjusted to steer droplets towards denser regions, thereby augmenting the likelihood of successful fertilization events.