The energy consumption in worldwide has been increasing rapidly, due to increase in world population. This energy consumption growth is apparently impacting on the environment and the society. This has accelerated the development and deployment of Renewable Energy Sources (RES) harvesting technologies and facilities. The global electricity production by RES by the end of 2016 is accounted to 24.4%. This increase in RES has highlighted the next big challenge, storage of energy when demand is lower than the supply. There are many energy storage technologies existing from decades. Battery technologies have the highest cost reduction potential at the moment. Battery technologies are delivering significant advances in a wide range of industries, from electrical vehicles to renewable power. From the discovery of electrical energy, there is a great need to store the electrical energy generated for use on demand. Energy Storage Systems (ESS) is used to store the excess electricity when a power production is greater than consumption. ESS play very important role for off-grid storage applications to back up Renewable Energy such as Solar and Wind power, used by people who live or work in remote areas. Electrical energy can be stored in different forms including Electrochemical-Batteries, Kinetic Energy-Flywheel, Potential Energy-Pumped Hydro, and Compressed Air (CAES). This paper gives the current state of battery storage technologies, its main challenges, its applications and actions for future.
The article analyzes the factors that accelerate the aging process of the oil-paper insulation of the condenser type and shorten its service life. Attention is drawn to the fact that the breakdown of flat insulation made of condenser paper occurs at the location of the inclusion, which approximately corresponds to the field of uniform field. An example of damage to the insulation of a current transformer due to its aging and moisture is given. This work was analysed the influence of thickness and density of paper, grade of mineral oil on short-term electrical strength. The characteristics of the insulating papers of the permeable composition largely determine the electrical strength of the paper-oil insulation.Since paper-oil insulation consists of a series of successive layers of paper and oil, it is advisable to present such insulation by the equivalent scheme shown in fig. 1, in which the thickness of the paper-oil dielectric is divided into two layers: paper (fiber) and mineral oil, connected in series. a) b) FIGURE 1.Equivalentpaper-oilinsulationscheme: a -tocalculatethevoltageontheoillayer;btocalculatethedielectriclossininsulation.The increase in the dielectric constant of the paper is accompanied by an increase in the tension in the oil layers of paper and oil insulation, which promotes the development of discharges in these layers and facilitates the breakdown of the insulation. As a result, the effect of paper density has a different effect on the short-term and long-term strength of the insulation. In determining the short-term strength, the influence of the first factor prevails, which contributes to its increase with increasing paper density. For example, by increasing the density of paper from 0.7 to 1.3 g/cm 3 , the electrical strength of sheet insulation (flat samples) increases by 60%.However, in determining the long-lasting strength, partial breakdowns in the oil layers lead to considerable destruction of the insulation. In this case, as the paper density increases, the breakdown strength is reduced and the insulation life is shortened.
The film-impregnated dielectric under operating conditions is subject to prolonged exposure to electric and thermal fields, as well as mechanical loading. In addition to critical partial discharges, the most serious drawback that impairs the film and condenser reliability in general is the deterioration of the electro-physical characteristics of the polypropylene film and liquid dielectric due to the gradual dissolution of the polymer in the liquid dielectric, which is determined by their chemical composition. This interaction of components, which was investigated in detail, has a thermo activation nature, which relates to the processes of rearrangement of atoms or molecules with the overcoming of potential barriers, and is manifested in the swelling of the polypropylene film with subsequent dissolution of the amorphous component in the polymeric component. As a consequence, irreversible structural changes of the film occur, which lead to a decrease in its electrical and mechanical strength, as well as to an increase in the dielectric loss of the liquid dielectric. Capacitor (Fig. 1 (a)) is designed to provide high-frequency communication at frequencies from 24 to 1500 kHz in power lines with a nominal voltage of 35, 110, 150, 220, 330, 500 kV AC 50 and 60 Hz. Coupling capacitor impregnated with environmentally friendly liquid -condenser oil. The short-circuits consist of capacitor sections (Fig. 1 (b)): a thin layer of dielectric is laid between two thin wide metal strips, and the dielectric film is placed on top and below the metal strips -capacitor covers. This paper gives the detail analysis of dielectric properties of capacitor paper. a) b) FIGURE 1.a) Capacitor connection; b)capacitor section and condenser paper for extra insulation between sections
The article draws attention to the fact that nowadays the demand for energy is not decreasing, but its cost is increasing. The need to research the parameters of photovoltaic modules and the capabilities of microprocessor technology for this is substantiated. It is noted that the scheme of electric distribution networks has become more difficult to operate, and the algorithms and methods of reliable and optimal management of modes are changing due to the modernization of the infrastructure of electricity supply and electricity consumption of the district. Nowadays, renewable energy sources are installed in the electrical distribution system at various levels of power supply and power transmission between the substation and consumers. Due to damage to the electrical equipment, there may be interruptions in the power supply, which unintentionally cause "islanding". During operation, situations sometimes arise when the power supply system of the "islands" is promptly de-energized starting from the points of connection of the "islands" to the unified electric power system. This happens based on the results of measuring the parameters of the mode of local electric power systems or based on the results of mathematical modeling of processes in local electric systems when, for example, the current levels of nodal voltages will not allow the use of an "island" electric network. For the purpose of researching processes in local electrical systems with photovoltaic plants, the article proposes their physical model in the form of a research bench, which can be used during the practical training of future employees who will manage the modes of distribution electrical networks with photovoltaic plants and maintain the equipment of such networks, systems and electrical stations Algorithms for optimal management of generated power, consumption and accumulation of electric energy tested using the proposed stand are designed to show the operating personnel ways of high-quality operation of distribution electric networks under the conditions of implementation of the Smart Grids concept.
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