Phase noncontact method and procedure for measurement of axial displacement of electric machine’s rotor

Today, the vast majority of technological processes, both production and agriculture, are based on the use of electric machines. Among which, a significant part of production equipment requires the use of electric motors, the power of which exceeds hundreds of kilowatts. Such electric machines have also become widespread as generating equipment, where they are an integral part of power plants, both using traditional energy sources (thermal power plants, nuclear power plants, etc.), and renewable (hydroelectric power plants, wind farms, etc.), where the unit power of a single electrical machine is usually higher than in other sectors of economy. When operating such equipment, systems for monitoring a significant number of technological parameters are often used, and in real time it characterizes the modes of their operation. This approach makes it possible to increase the reliability of operation and, with a fairly high probability, to avoid large-scale man-made threats that can be caused by an emergency failure of power electric machines (including powerful electric generators), which are quite often accompanied by the destruction of supporting structures, structural elements of industrial premises and can pose a threat to the life and health of production personnel. But the use of even the most modern systems for monitoring the technical condition does not provide one hundred percent reliability, and when operating electrical machines with a nominal power of the order of units of MW Today, the vast majority of technological processes, both production and agriculture, are based on the use of electrical equipment. A similar situation occurs in the household sector, where we can also note a significant increase in energy consumption in recent decades. Given this, it is obvious the need to ensure the transfer of significant amounts of electricity, which is not possible without the use of transformers and power electric devices, the construction of the lion's share of which provides insulation of live parts and excess heat using transformer oil. Such equipment, in particular, includes: oil transformers, oil and low oil switches, which are characterized by a relatively low cost at sufficiently high rated currents and voltages. One of the most significant disadvantages of this equipment is the need for constant monitoring of the condition of transformer oil, the physical properties of which largely determine the dielectric strength and overload capacity of the equipment as a whole. The mass fraction of moisture in the latter is one of the key indicators that determine its dielectric and thermally conductive properties. Therefore, the existing technical regulations for the operation of the latter provide for regular laboratory examination of the physical properties of the latter during the technical inspection of equipment, which usually requires quite a lot of time. In turn, this leads to an increase in economic losses associated with increasing the duration of planned maintenance work. Therefore, given the above, it is obvious that the development of new high-precision means of rapid measurement of transformer oil humidity is an urgent task of considerable practical interest. The article presents a mathematical model of a transformer oil sample, which establishes an unambiguous relationship between its humidity and integral dielectric conductivity in the range of humidity changes from 0% to 0.6%, which corresponds to the allowable moisture content in the latter. It is shown that the obtained functional dependence of the integral dielectric constant on moisture within the investigated range has a monotonically increasing character. Also, the design of a high-frequency humidity sensor based on a band asymmetric wave-water wave was developed, in which the primary measuring conversion of humidity into the amplitude of the output electromagnetic wave is carried out. A mathematical model of such a sensor is developed and the transformation equation is obtained. To confirm the adequacy of the theoretical conclusions, an experimental study was conducted, based on which it was found that the total relative error does not exceed 2%.

Mathematical Model of the Primary Measuring Converter of Humidity Transformer Oil

Hraniak

Yemchyk

Kozhushko

2022

Dielkometrical Transformer Oil Humidity Sensor

Hraniak,

Voznitskyi

2023

Self Cite

It is known that water is part of the vast majority of organic and inorganic materials. Materials formed in natural conditions or obtained in the production process, as a rule, contain a certain amount of water in their composition, the mass fraction of which depends both on the ability of the material to absorb (sorb) or retain on the surface (adsorb) water, and on the conditions, in which this phenomenon takes place. Moisture content significantly affects the physical and electrical properties of non-metallic materials, including transformer oil. In particular, the increase in moisture content in the latter not only significantly reduces its dielectric strength, creating prerequisites for a breakdown between the current-carrying parts of transformers, oil switches and other equipment that involves its use. Regular measurements of the humidity of transformer oil are an essential component of the maintenance of a whole group of electrical equipment. And since nowadays the transition from planned maintenance to on-demand maintenance is becoming more and more widespread, it can be concluded that the development of means of controlling the humidity of transformer oil, which would be suitable for high-precision express measurement or work compatible with control systems in the mode real time is an actual scientific and applied problem. The article proposes the construction of a transformer for measuring the dielectric loss tangent angle of transformer oil, which is characterized by increased metrological characteristics and is suitable for real-time operation. The value of the tangent of the dielectric loss angle of the transformer oil measured with the specified measuring transducer, being related to the humidity of the latter by the corresponding functional dependence, can be used for the analytical determination of the latter. A mathematical model of the dielectric angle tangent measuring transducer has been developed, on the basis of which both the sensor conversion equation and other metrological characteristics can be estimated.

Features of the Influence of the Technical Parameters of Asynchronous Motor on the Formation of It's Three-Phase Stator Current System

HRANIAK,

KUPCHUK,

ZLOTNITSKYI

et al. 2024

In recent decades, there has been a growing trend towards the increasing role of automated electric drives implemented based on asynchronous motors. This trend is driven by several objective factors, among which the main ones are the development of mathematical models of asynchronous motors, leading to increased accuracy and functional capabilities of their control systems, and active advancement in power semiconductor technology, resulting in improved efficiency and reduced cost of power frequency converters. It is worth noting that a consequence of modern technical progress is the increase in complexity, cost, and technological sophistication of industrial equipment, thus leading to potential losses accompanied by its malfunction during operation. Another trend in the development of industry, both in Ukraine and in most industrially advanced countries, is the increase in the quantity of electrical equipment that has reached its nominal service life. Since there is an inverse proportional relationship between reliability and operating time of rotating electric machines, it is quite logical and evident that this leads to the growing relevance of building highly efficient systems for their diagnostics. The article justifies the expediency of applying current-based diagnostic methods for asynchronous motors, which do not require intervention in the construction of the electric machine, allowing simplification of the design of the diagnostic system and reducing capital costs for its construction. It also theoretically substantiates the functional relationship between the technological parameters of an asynchronous motor and the frequencies of the components of the current signal of its stator circuit, on which their influence will manifest, which in perspective will allow identifying abnormal deviations from the corresponding technological parameters by monitoring the harmonic components of the stator current.