A. A. Shayegani

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In this paper the measuring results of polarization and depolarization currents (PDC) on oil-pressboard samples will be presented. The measurements were carried out under different condition and the results compared. For repeatability purpose the samples were provided at specific condition. Moisture of samples was measured by Karl Fischer titration method.(More)
Compared to HVAC, the application experience of composite/polymer insulators in HVDC transmission lines is limited. However, the tendency to utilize them in HVDC transmission lines, where pollution flashover is a major problem, is growing due to their water-repellent feature. This trend demands understanding insulator flashover performance and recognizing(More)
Conventional loss factor and capacitance measurements are used to determine condition of insulating liquid. In the new IEC 61620 standard capacitance and conductance are measured at low voltage and low frequency with square wave method to over come some difficulties of the conventional method. Nowadays low frequency dielectric spectroscopy becomes a(More)
Experimental and computational images of a 90-&#x03BC;m thick copper wire explosion in atmospheric pressure air are presented. A Marx generator is used to produce a pulsed current density into the wire with a maximum rate of rise of ~ 10<sup>18</sup> Am<sup>-2</sup> s<sup>-1</sup>. A multiphase numerical model includes mass and momentum conservation(More)
This paper demonstrates the use of a dielectric spectroscopy technique for monitoring the effect of different ageing: ultra violet radiation (UV), thermal, water immersion, humidity and water boiling on silicone rubber, ethylene-propylene diene monomer (EPDM) and alloy of SIR-EPDM (50/50 wt%). The measurement of dielectric constants and dielectric losses in(More)
Environmental and electric stresses have great ageing impacts on the polymer insulators. Ultraviolet (UV) radiation is one of the most important environmental factors that affects the degradation of Silicon Rubber (SiR) insulators. This paper presents the accelerated ageing records of a 20 kV SiR insulator in a chamber containing nine UVC lamps with(More)
As an integral part of transmission lines, insulators play a major role in the reliability of power systems and their failure exposes the performance of the whole system into risk. Compared to AC systems, DC static field and corresponding arc without zero crossing makes DC flashover performance more problematic. Although the utilization of composite(More)
A detailed model was presented to explain the dielectric barrier effects employed to improve the insulation performance. The simulations were carried out for the dielectric barrier in two forms; as coating on electrodes, and as insertion in the inter-electrode gap. The electron conservation was modeled by the electron number density continuity equation(More)
Ultraviolet (UV) aging is one of the most important problems that electrical insulations are faced with it. Generally, total UV radiation emitted from the sun is divided into three parts. Among all types of ultraviolet radiation, UV<sub>C</sub> has the highest energy because its wavelength is less than 290 nm. Therefore, UV<sub>C</sub> is definitely harmful(More)
—In case of wet pollution, pollution layer create an appropriate path for leakage current and increasing of this pollution leads to more values of this leakage current. Therefore for better recognition of insulator changing process from normal state to fault outbreak, studying of leakage current and artificial aging models is necessary. In this paper, the(More)