Elektrotehnìka ta Elektroenergetika (Dec 2018)
ANALYSIS OF THE SHOP NETWORKS BASBURS PARAMETERS AT HIGHER HARMONIC CURRENT ACTIONS
Abstract
Purpose. Research and analysis trolley busbar’s parameters in condition of higher current harmonic actions, with taking into account the structural features of nonlinearity of magnetic and electrical properties of materials, proximity effects, surface and external surface effects. Methodology. The researches were carried out using the electromagnetic field theory methods, the electrical circuit theory, mathematical physics, finite elements, interpolation, approximation and regression analysis. Findings. The voltage drop in the phases of busbar’s trolls from the action of higher current harmonics is researched. It has been evidenced that with permissible values of higher harmonics established by the standard for different short-circuit ratio Rsce, the magnitude of the voltage drop can increase by 3.5 times, and using the steel casing - by 4 times. At the same time, the increment of the magnetic field energy and active losses in the busbar is 20% relative to their values for the main current harmonic, excluding shielding, and up to 23%, including shielding of busbar’s trolleys. The action of higher harmonics at permissible own amplitudes at corresponding values of the short-circuit ratio Rsce also causes an increase in active resistance by 4 times, inductive - by 20 times. Due the features of the placement of the busbar in the workshop, production and technological processes, the shielding of the busbar’s trolleys is required. Therefore, in such cases, to compensate for the asymmetry of the voltage drop in the trolleys and active losses in the busbars, the current load of the busbar’s trolls should be reduced by 5-20% depending on the value of the short circuit coefficient of the shop network. Originality. The mathematical model of electromagnetic processes in the copper busbar’s trolley, which contain design features, nonlinearity of magnetic and electrophysical properties of materials, proximity effects, surface and external surface effects, the effect of current harmonic components on voltage drop and power loss in the power transmission are proposed. It allows with high accuracy and numerical efficiency, to determine the busbar’s trolley parameters for the corresponding values of the amplitudes and frequencies of the current hight harmonics. For the first time, the relationship between the voltage drop and specific active losses from the spectrum of frequencies and amplitudes of current harmonics and the values of the short-circuit coefficient is executed, which allows to determine the degree and character of the effect on the asymmetry of the voltage drop and the parameters of the busbar’s trolley. Practical value. It has been evidenced that with permissible values of higher harmonics established by the standard for different short-circuit ratio Rsce, the magnitude of the voltage drop can increase by 3.5 times, and using the steel casing - by 4 times. At the same time, the increment of the magnetic field energy and active losses in the busbar is 20% relative to their values for the main current harmonic, excluding shielding, and up to 23%, including shielding of busbar’s trolleys. The action of higher harmonics at permissible own amplitudes at corresponding values of the short-circuit ratio Rsce also causes an increase in active resistance by 4 times, inductive - by 20 times. The results of the work can be used in the design or modernization of existing shop power supply systems, as well as to determine the parameters, as well as to estimate the voltage drop in the other busbar’s design.
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