Introduction. Measurements on alternating current of dielectric absorption parameters-capacitance and dielectric loss tangent tgδ allow us to evaluate the quality of insulation of cables, electrical machines, transformers, etc., both at the technological stage of manufacture and in operation. An increase in the reliability of the measurement result of the parameters is provided by a decrease in the measurement error due to the improvement of measuring instruments and measurement methods and an increase in the number of measurements Purpose. The estimation of the error of control of electrical insulation structures by dielectric absorption parameters in accordance with the concept of measurement uncertainty. Methodology. The error of measurements of the capacitance and the tangent of the dielectric loss angle is estimated using the example of a twisted unshielded pair of category 5e. A statistical analysis of the results of multiple measurements of the capacitance and the tangent of the dielectric loss angle of an unshielded cable is carried out. The linear regression equations for the measured values of the dielectric absorption parameters of the number of measurements are obtained. Practical value. Ensuring unity in the methods for estimating the error of measurement results, both when using the traditional concept of «measurement result error» and when introducing the concept of «measurement result uncertainty» into practice, it will allow to unambiguously interpret and correctly compare the results of measurements of the capacitance and tangent of the dielectric loss angle of electrical insulation structures. References 16, figures 3.

Introduction. In the objects of control there are always a number of interfaces, for example, solid insulation -electrode. On contacting surfaces, free surface charges are transferred. Surface conductivity leads to fluctuations in the measured values of the capacitance and the tangent of the dielectric loss angle of solid insulation, the state of which is determined. The drain off of the surface charge does not lead to a decrease in the scatter of the measured dielectric absorption parameters. One of the main reasons for the significant time spread of the dielectric absorption parameters, and to a large extent (three orders of magnitude) of the dielectric loss tangent are tribo charges caused by triboelectrification of cable structural elements. Tribo charges cause internal noise in electrical insulating structures, masking processes in the polymer insulation itself. Purpose. Substantiation of a method for analyzing the time series of dielectric absorption parameters, which provides increased accuracy of control and diagnostics of solid polymer insulation of electrical insulation structures based on filtering experimental data using wavelet transform. Methodology. The inefficiency of filtering the spectra of time series using a low filter based on the direct Fourier transform is shown. Multilevel wavelet decomposition of the time series of parameters is presented, and the efficiency of applying wavelet transforms to identify high-frequency and low-frequency components in the measured values. Practical value. The method of analyzing the time series of dielectric absorption parameters using the wavelet transform, proposed for the first time, makes it possible to increase the accuracy of monitoring and diagnostics of solid polymer insulation both at the manufacturing stage and in the operation of electrical insulating structures. This method is the basis for creating a database of control results for assessing the state of solid polymer insulation of electrical insulation structures, in particular, power and information cables.References 17, figures 8. Key words: dielectric absorption parameters, capacitance, dielectric loss tangent, spectrum of time series, low-pass filter, decomposition levels, approximation and detail, wavelet transform. Встановлено вплив поверхневих і трібозарядов на результати контролю ємності і тангенса кута діелектричних втрат екранованих і неекранованих кабелів з полімерною ізоляцією. Показана неефективність фільтрації спектрів часових рядів за допомогою фільтра низьких частот на основі прямого перетворення Фур'є. На прикладі неекранованого кабелю представлено багаторівневе вейвлет розкладання часових рядів параметрів і показана ефективність застосування вейвлет перетворення для виявлення високочастотних і низькочастотних компонент у виміряних значеннях. Обґрунтовано оптимальний рівень розкладання параметрів діелектричної абсорбції неекранованого і екранованого кабелів за допомогою вейвлета Добиші 12 порядку. Доведено ефективність методу вейвлет аналізу часових рядів параметрів діелектричної...

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Introduction. The wave parameters of power cables with polymer insulation differ significantly from the parameters of overhead lines and power transformers. As a result, there are more and more objects in electrical networks for which the occurrence of complex multi frequency transients, accompanied by dangerous overvoltages, should be expected. Purpose. To develop a computational model of the complex impedance of high-voltage single-core power cables of coaxial design required to determine the frequency dependencies of the active resistance and inductance of the conductive core and metal shield, taking into account the surface effect and proximity effect. Methodology. The method is based on solving a system of linear algebraic Kirchhoff equations (SLAE) for magnetically coupled contours. SLAE can be used to calculate conductors taking into account the skin effect and proximity effect. Practical value. The developed model is the basis for determining the characteristic impedance of high-voltage single-core power cables in a wide range of frequencies required to establish adequate criteria for evaluating the parameters of high-frequency effects critical for cross linked polyethylene insulation.

This paper presents a substantiation of an approach for direct measurements of dielectric dissipation factor of layers of insulation between the conductors of three-core power cables. Proposed approach is based on grounding of the inspecteddielectric layer through the sufficiently low electrical resistance. The results of carried out analysis, which was carried out taking into consideration the presence of numerous parasitic parameters of tested layer of insulation due to the capacitive coupling between the electrically conductive elements of three-core power cable, have shown that for the case of sufficiently low value of used resistor the value of phase shift between the waveforms of voltage drop on inspected layer of insulation and resistor, through which this layer of insulation is grounded, coincides with the value of phase shift between the sine waveforms of current and voltage for parallel equivalent scheme of tested layer of insulation with power losses. Because of the dependence of dielectric power loss angle on the value of phase shift between sine curves of current and voltage, the presented approach for the measurement of dielectric dissipation factor is based on such coincidence of values of phase shift. Depending on the value of applied resistor, the value of dissipation factor is calculated on the basis of measured value of phase shift between the voltage drop on the electrical resistor, through which tested layer of insulation is grounded, and either the waveform of voltage dropon the inspected layer of insulation, or the waveform of applied voltage. Factors that affect the accuracy of measurement are discussed, equivalent schemes of tested three core power cable for various ways of applying testing voltage are presented and theexample of practical implementation of presented approach for dissipation factor measurement is also given. Further development of presented approach for dissipation factor measurement is supposed to include the comparative analysis of the results of its practical implementation with the results obtained by applying previously developed techniques based on aggregate measurements.

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Quadrature phase shifters are widely used in practice of development of measurement systems intended for the measurements of dielectric dissipation factor and electrical capacitance. This article presents the examples of implementation of phase shifters intended to obtain the value of phase shift equal to 90º for the applying in measurement systems of monitoring and diagnosing the technical condition of electrical insulation. The developed solutions are based on applying of the analog signal multiplier implemented in the AD633 integrated circuit. The required value of phase shift is provided by adding a pre-shifted at a certain angle input harmonic signal to a signal with the reduced amplitude and the opposite initial phase. The article is also focused on the development of schematic solutions which can be used in order to remove the undesirable for many practical applications discrepancy between the amplitudes of the input and the output signals. This alignment of amplitudes is provided by the detection of their average rectified values with subsequent multiplication of their ratio by the shifted at 90º signal with the reduced amplitude. The designed schematic solutions imply the applying of analog circuits which contain the input phase shifter, low pass filter, voltage summing amplifier, two detectors of average rectified values, three analog multipliers and one voltage divider.