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The microwave dielectric properties of binary composites made by high dielectric constant ceramic fillers and polyethylene matrix are studied in this paper. Three ceramic powders of fillers with dielectric constants of 100 and 170, respectively, are adopted. The experimental dielectric constants of ceramic dispersions in the polyethylene matrix at microwave frequencies of 5 to 10 GHz are compared...
This paper reviews the use of fuzzy logic (FL) for dissolved gas analysis (DGA) of mineral oil for power transformer fault diagnosis (PTFD). A brief overview of conventional PTFD techniques using DGA of mineral oil is firstly surveyed. Then, applications of FL techniques for PTFD reported in international journals for evaluating power transformer conditions are extensively reviewed. Various FL techniques...
Polyimide film, as a special type of engineering plastic film, is a kind of basic insulating material and is widely applied in the aerial, nuclear, microelectronic industry, turn to turn insulation and turn to ground insulation of inverter-fed motors. However, premature insulation failures occur frequently in motors with the disadvantage of pure PI inherent in all organic materials. The existence...
Power cable grids have been growing enormously over the years; due to their aging, there is a strong need for Partial Discharge (PD) measurement techniques in order to identify incorrectly installed or damaged cable joints or cavities in cross-linked polyethylene (XLPE) insulated and paper-insulated lead-covered (PILC) cables. Mixed power cable systems consist of a mixture of interconnected cables...
This paper presents a novel and efficient method to estimate the optimal blend of Silicone Rubber (SiR) and Ethylene Propylene Diene Monomer (EPDM). The SiR and EPDM are widely used insulating materials. Blending of these polymers is one way of obtaining a new material with superior properties of both. Hence blending of SiR/EPDM with different blend ratios has been done. These blends are tested for...
The addition of conducting nano-particles has resulted in interesting properties of the resultant polymer composites. Considering the properties of carbon nano-tubes (CNTs) their inclusion in polymer composites should vastly increase the performance of the resultant composite. However, this is not the case due to the poor interfacial adhesion of the CNT and polymer matrix. The present study focuses...
The article presents the results of extensive investigations aimed at determining the moisture content in a large population of power transformers (161 units). The project was carried out during the period of 2003??2011 in Poland, Germany, and Sweden. All results were obtained by means of the Frequency Response Spectroscopy (FDS) method. Among the transformers tested were grid transformers, generator...
We discuss the modeling of dielectric responses of electromagnetically excited networks which are composed of a mixture of capacitors and resistors. Such networks can be employed as lumped-parameter circuits to model the response of composite materials containing conductive and insulating grains. The dynamics of the excited network systems are studied using a state space model derived from a randomized...
A new dielectric breakdown measurement method for determining breakdown characteristics of polymer films has been developed and evaluated. The method is based on measurement of multiple breakdowns per sample area beyond the weakest point of the film by utilizing low-energy self-healing breakdown of metallized polymer film. A data selection process based on the discharge energy characteristics of each...
With the integration of data and information obtained from a variety of chemical and electrical tests on transformer insulating oil, it is possible to evaluate the health condition of the insulation system of an in-service power transformer. This paper develops an intelligent algorithm for automatically processing the data collected from oil tests and determining a health index for the transformer...
With the increase of operation voltage to 800 kV-1100 kV, the sphere-plane gaps with radius of 0.5-1 meter are widely used in the converter station of UHVDC power transmission system. In order to ensure the safety of UHVDC system and reduce the investment, it is necessary to investigate the breakdown characteristic of large radius sphere-plane gap. This paper implemented experiments on three different...
The strength of electrical insulation in gaseous compressed SF6 is determined by various parameters, like pressure, polarity, field homogeneity, surface roughness of the electrodes, particulate contamination, and voltage wave shape. The dependence of the involved physical phenomena on accessible design parameters, like e.g. pressure, geometry, is of interest for the prediction of partial discharge...
Dielectric response measurements are an important technique to characterize dielectric materials. However, the electrode arrangements as well as the accuracy of the measurement setup limit the precision of this characterization, especially in case of solid dielectric materials. An air reference method and a contact-free electrode arrangement are described in this paper to enhance the dielectric characterization...
A study of the emission spectra from discharges on an ice surface and a discussion of its implication on local thermodynamic equilibrium are presented. Rotational temperatures were measured using OH (A-X) emission bands. The variation of rotational temperature, which is similar to that of gas temperature with discharge current, was studied. The excitation temperature of the arc column was determined...
Partial discharge (PD) characteristics of hexadecane were studied in a needle-plane electrode geometry under AC field with a 20 μm tip radius tungsten needle. PD experiments were conducted on samples containing known concentrations of aromatic and corrosive sulfur compounds. Partial discharge inception voltage (PDIV), streamer repetition rates, and phase resolved PD (PRPD) patterns were acquired....
Composite insulators have been used in power system for more than 20 years in China. Compared to porcelain and glass insulators, the pollution flashover performance of composite insulators is better, whereas the icing flashover performance is worse. Shed configuration is a key factor that influences flashover voltage of composite insulators covered ice or snow in icing regions. The DC flashover tests...
The flashover phenomenon for the unilluminated case along the interface of solid dielectric in vacuum is the main factor which restricts the performance of high pulsed power devices, and there are plenty of investigations devoted into determining which parameters are important in predicting flashover behavior and the theoretical understanding involved in the process in the past several decades. In...
In this paper, polydimethylesiloxane (PDMS) as a candidate for high voltage insulation applications is investigated as to the aging behavior at different temperatures in air. Three models according to ISO 11346, to Gillen et al, and to Hoang and Lowe were applied to determine endurance limits in terms of a time-to-failure after aging in hot air. Aging was performed in air from 150 to 170°C. Tensile...
On the background of the peculiar technology problems with the external insulation of UHV dc equipment in China, caused by high altitude and heavy pollution, this paper presents the pollution flashover performance of full-scale ??800 kV converter station post insulators at actual high altitude area. The tests were carried out according to the solid layer method, and the 50% withstand voltage (U50%...
Transformer mineral oil has been replaced by alternative oils such as synthetic oil and natural esters due to their biodegradability and environmentally friendly nature. This paper presents performance of coconut oil as such an alternative. Generally, as the other alternative oils, coconut oil has high conductivity due to the presence of free fatty acids. In this study, three different types of coconut...
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