Characteristics Of Transformer Research Articles

The Impact of Rotor Torques for the Pressure Ratio Characteristics of the Double Rotor Hydraulic Transformer

Serving as a core component, the performance of the hydraulic transformer (HT) directly affects the energy-saving performance of the common pressure rail (CPR) system. The HT is capable of both amplifying and reducing pressure without throttle loss, in which the pressure ratio is a critical parameter controlled through adjusting the torques acting on the rotors. However, our understanding of it relies on simplified models due to the complicated operation mechanism. This study focuses on the pressure ratio characteristics of the novel double rotor hydraulic transformer (DRHT). Firstly, the key influencing factors of the DRHT are acquired through theoretical analysis. Secondly, a dynamic model of the DRHT is established allowing for mechanical and fluid properties. Thirdly, a specially designed DRHT prototype is manufactured and the test bench is built up to verify the model. The experimental and numerical results show that the pressure ratio varies nonlinearly with the control angle especially when the control angle is greater than 10 degrees, while it changes almost linearly with the increasing rotating speed. The test results are consistent with the simulation results, which credit the mathematical model feasible and effective. The parametric study show that the augment of the A slot wrap angle on the valve plate could enhance the driving torque, as a result larger pressure ratio can be acquired. The enlargement of the B slot on the valve plate could make the variation of the pressure ratio more linearly. The current work is also significant for further design and the application of the DRHT.

Investigation of factors influencing the operational characteristics of traction transformers

This article presents the results of visual inspections and a brief statistical analysis of the data obtained in order to identify the observed defects in traction transformers of ODTsE 5000 / 25 B and OTsR 5600/25 types in operation in the railway system. The analysis revealed that the main parameters that determine the operational characteristics of traction transformers are windings and insulation. Recommendations for the prevention of faults in traction transformers and increase their service life have been developed.

Research on Multi-Port DC-DC Converter Based on Modular Multilevel Converter and Cascaded H Bridges for MVDC Applications

Aiming at the low-voltage DC distribution network system and combining the characteristics of F2F structure and ISOP-DAB structure DC transformer, this paper proposes a DC transformer structure based on modular multilevel converter (MMC) and cascaded H-bridge. First of all, this paper analyzes several different cases. Case 1 proposes a type of equal carrier-phase-shift pulse-width modulation (CPS-PWM) of MMC, which can produce an equal five-level voltage waveform. In the meanwhile, another unequal CPS-PWM control is proposed to produce an unequal five-level voltage waveform. According to the descriptions of case 2 , the quasi-square-wave-modulation method with a wide gain range can greatly reduce the insulation design difficulty of the intermediate AC side high-frequency transformer and the voltage stress on the AC side. Case 3 demonstrates the extended-phase-shift (EPS) control of three-port DC-DC converter. Combining the voltage sorting algorithm of voltage sequencing and cyclic switching, a strategy of voltage equalization for grouped capacitors is proposed. Considering the various application scenarios of actual working conditions, the soft switching characteristics and multi-port power characteristics of the DC transformer are analyzed. In order to verify the feasibility of the DC transformer structure and its control strategy, a simulation model was built in Matlab/Simulink and the results were verified. The results are in accordance with the theoretical analysis.

Experimental obtaining characteristics of current transformers for developing their models and determining the time of saturation of the magnetic circuit

Electromagnetic current transformers (CT) are subject to saturation and residual magnetization of a magnetic circuit. This phenomenon has an impact on the operation of devices of commercial accounting of electric energy and relay protection and automatics (RPA). Saturation of the current transformer’s magnetic core can lead to emergency situations due to incorrect operation of the protections and excessive disconnection of the protected connections. At the moment, Russian norms do not regulate the work in transient modes, including short circuits with an aperiodic current component. The Ivanovo State Power Engineering University (ISPEU) conducts research on the topic of determining the time to saturation of CT at short circuit. The purpose of the work was to develop an algorithm for monitoring saturation and determining the time to saturation of the CT magnetic core, in order to ensure the correct operation of the RPA in all modes. The article is devoted to the method of construction and research of mathematical models of CT for calculating the time to saturation. The general structure of the algorithm for determining the time to saturation is presented.

Research on Pressure-based Detection Technology for Partial Overheat Insulation Defect of Oil-less Power Equipment

Pressure monitoring technology is the current state monitoring research hotspot of oil-less power equipment. Aiming at the lack of pressure change characteristics caused by overheating insulation defect of oil-less power equipment, this paper studies the pressure change characteristics of 110kV oil-immersed power transformer under local overheating insulation defect. Overheating defect belongs to the low temperature overheating, temperature rise gradient is 50 °C . Analysis of the experimental results indicates that pressure change trends show exponential, in the initial stage, the pressure increased sharply, then it increased slowly, and finally it tended to be stable; the increase of pressure in 50 hours ranged from 1kPa to 3kPa, and the pressure increase was obvious, which indicated that the online monitoring of local overheating insulation defects of the casing could be achieved by pressure monitoring technology, and finally the casing pressure change law was analyzed theoretically.

Reliability of an Automatic Adjustable Current Transformer

In the article the reliability calculations of automatic transformers with adjustable range are performed. Since reliability is one of the main characteristics of current transformers, several parameters of its range are included in the calculation of the reliability of an automatic adjustable current transformer, and as a result, high-precision values of reliability were achieved.

Power transformer life analysis based on Lambert W function

As the core equipment of many construction electric fields, reasonable life management of power transformer plays an important role in ensuring the safety production and economic benefits of public and enterprises. Based on Lambert W function, the exact solution is obtained by calculating the annual apportioned total cost. The variable values that may have errors in the function model are deeply analyzed. Combined with the inherent characteristics of power transformer, the factors influencing the economic life in the results are analyzed. The reliability of this method is proved by an example. Compared with the traditional tabulation method, this method is convenient for further analysis of the influencing factors and changing rules of economic life. At the same time, this method can also be used in other equipment to study its economic life since the specific problems are analyzed. It has the value of popularization.

A novel characteristic optimization method based on combined statistical indicators and random forest for oil-paper insulation state diagnosis

In order to effectively utilize the dielectric response characteristics of transformers to diagnose the insulation state, this paper proposes a two-level hybrid optimization method for analyzing time-domain dielectric response characteristics. The optimization algorithm is based on the combined statistical indicators (CSI) and random forest (RF) theory. The initial feature space set is formed with 23 time-domain characteristics. In the first-level stage, statistical indices correlation, distance, and information indicator are integrated to assess the synthesis score of the characteristics, while highly redundant and low-class discrimination characteristics are eliminated from the initial space set. In the second-level stage, Random Forest based outside bagging data theory is introduced to evaluate the least important characteristics, and the characteristics with low importance indices are excluded to obtain the final optimal feature space set. The proposed method is carried out on 82 sets of data from actual dielectric response tests on oil-paper insulation transformers. Finally, the final optimal feature space set, along with several other data sets, is tested via different diagnosis methods. The results show that the optimal feature space set obtained via the proposed method outperforms other feature space sets in terms of better adaptability and diagnosis accuracy.

ANALYSIS ON THE OPERATION PARAMETERS OF THE NEW CONVERTER TRANSFORMER

This paper presents a new converter transformer which is applied in multipulse diode/SCR rectifiers/inverter. Comparison of operational characteristics of a conventional converter transformer and the proposed transformer was studied. Results show that the new converter transformer can not only decrease the grid side current, increase the valve side voltage but also greatly reduce the harmonics of the grid side currents. Simulation results verify the correctness of the theoretical analysis.

Wireless Power Transfer System with Ideal Transformer Characteristics Determined Solely by Coil Turns Ratio

Wireless Power Transfer System with Ideal Transformer Characteristics Determined Solely by Coil Turns Ratio

Моделирование процессов электронного усиления в каналах умножителей на пористых структурах оксида алюминия

The secondary-emission multiplier of spatial-distributed flows of electrons – microchannel membrane – determines along with the photocathode, luminescent screen, electron-optical system determines the amplifying characteristics of the electron-optical transformers, photoelectronic multipliers. This, in its turn, determines the application areas and the operating range of the items. The actual task is an improvement of the microchannel membrane parameters and the search for new approaches to manufacture on alternative materials of the secondary-emission multipliers. In the paper the use of self-organizing high-ordered porous anode structures of aluminum oxide as the secondary-electronic emitters have been considered. The theoretical and practical approaches to development and the implementation of the computer models of processes of multiplying electrons in the channel of the based on aluminum oxide, have been offered. Based on the results of the calculations, performed using this model, the amplifying ability of such channels has been determined, their optimal caliber is 25, and the supply voltage is 300 V. A comparative analysis of these characteristics of secondary electron multipliers with corresponding parameters of microchannel plates based on lead silicate glass has been performed. It has been determined that that porous anodized alumina may be suitable for the manufacture of secondary electron multipliers. Its secondary emission ability is comparable to lead silicate glass.

Analysis of Factors Affecting Temperature Rise of Oil-immersed Power Transformer

The key factors that affect the operation state of power transformer include thermal problem and insulation problem. It is of great significance to pay attention to the factors affecting the temperature rise characteristics of transformer to ensure its stable operation. The temperature rise characteristic model of transformer is established to explore the possibility of replacing mineral oil with plant insulation oil FR3 in this paper. On the basis of calculating the influence of ambient temperature change of external heat source on transformer temperature rise, the relative life loss rate of transformer under different ambient temperature is calculated. The results show that FR3 vegetable oil can replace mineral oil in terms of temperature rise. The temperature of the transformer core and winding hot spot increases with the ambient temperature. When the ambient temperature exceeds 293K, the relative life loss rate of the transformer increases very quickly. Therefore, the transformer should not be kept in an environment where the temperature exceeds 293K for a long time.

Ceramic-Heterostructure-Based Magnetoelectric Voltage Transformer with an Adjustable Transformation Ratio.

A voltage transformer employing the magnetoelectric effect in a composite ceramic heterostructure with layers of a magnetostrictive nickel–cobalt ferrite and a piezoelectric lead zirconate–titanate is described. In contrast to electromagnetic and piezoelectric transformers, a unique feature of the presented transformer is the possibility of tuning the voltage transformation ratio K using a dc magnetic field. The dependences of the transformer characteristics on the frequency and the amplitude of the input voltage, the strength of the control magnetic field and the load resistance are investigated. The transformer operates in the voltage range between 0 and 112 V, and the voltage transformation ratio K is tuned between 0 and 14.1 when the control field H changes between 0 and 6.4 kA/m. The power at the transformer output reached 63 mW, and the power conversion efficiency was 34%. The methods for calculation of the frequency response, and the field and load characteristics of the transformer are proposed. The ways to improve performance characteristics of magnetoelectric transformers and their possible application areas are discussed.

Experimental study of vibration characteristics of 110 kV oil-immersed transformer

As the voltage level and capacity of power transformer continue to rise, this results in its increasingly prominent vibration and noise problems. In this article, we study the vibration characteristics of the 110-kV oil-immersed transformer by means of experiments. Under different no-load voltages and short-circuit currents, the vibration signals in different positions and directions of the transformer are monitored respectively, and the vibration laws are analyzed. First, the vibration law of transformers is closely related to the operating conditions of transformers, which directly affects the frequency components of transformer vibration and the amplitude corresponding to different frequencies; second, it is found that the vibration law of transformers facing different directions will change under different operating conditions; and third, it summarizes the vibration of transformers in different positions under different operating conditions. These results can not only be used as the experimental basis for the theoretical research on large-scale transformer noise but also provides experimental support for the research on vibration reduction and noise reduction methods of large-scale transformer in engineering.

Enhancement of the Thermal Performance Characteristics of an Electrical Power Transformer

A 3D numerical simulation was conducted to test the effects of the geometrical and operational parameters on the cooling performance of a three-phase electrical distribution transformer (250 kVA oil natural air natural (ONAN)). The geometric parameters include the shape of the transformer (rectangular, circular, and hexagonal), fins shape (rectangular, semicircular, and trapezoidal) as well it arrangement (asymmetric fin heights and perforated fins). Both of oil temperature and thermal load have been used as boundary conditions. In order to verify the reliability of the numerical model, comparison between numerical results and experimental finding has been done. The results have indicated that the circular and hexagonal shapes reduced the average oil temperature by 3.4% and 4.7%, respectively, compared to the traditional transformer shape (rectangular). Furthermore, the lowest average oil temperature was observed for the trapezoidal fin, followed by the rectangular and semicircular fins. Additionally, it has been noticed that the asymmetric fin heights of the trapezoidal and perforated trapezoidal fins been contributed to the improvement of the cooling performance of the transformer. Furthermore, the best thermal performance was obtained with the trapezoidal perforated fin to compared other arrangement of fins. Finally, the highest reduction in oil has been obtained by the use of hexagonal transformer with a perforated trapezoidal fin approximately by 12% compared to traditional rectangular transformer. Hence, it can be concluded that the shape of the transformer and fins play an important role in thermal performance of such systems.

Enhancement of the Thermal Performance Characteristics of an Electrical Power Transformer

A 3D numerical simulation was conducted to test the effects of the geometrical and operational parameters on the cooling performance of a three-phase electrical distribution transformer (250 kVA oil natural air natural (ONAN)). The geometric parameters include the shape of the transformer (rectangular, circular, and hexagonal), fins shape (rectangular, semicircular, and trapezoidal) as well it arrangement (asymmetric fin heights and perforated fins). Both of oil temperature and thermal load have been used as boundary conditions. In order to verify the reliability of the numerical model, comparison between numerical results and experimental finding has been done. The results have indicated that the circular and hexagonal shapes reduced the average oil temperature by 3.4% and 4.7%, respectively, compared to the traditional transformer shape (rectangular). Furthermore, the lowest average oil temperature was observed for the trapezoidal fin, followed by the rectangular and semicircular fins. Additionally, it has been noticed that the asymmetric fin heights of the trapezoidal and perforated trapezoidal fins been contributed to the improvement of the cooling performance of the transformer. Furthermore, the best thermal performance was obtained with the trapezoidal perforated fin to compared other arrangement of fins. Finally, the highest reduction in oil has been obtained by the use of hexagonal transformer with a perforated trapezoidal fin approximately by 12% compared to traditional rectangular transformer. Hence, it can be concluded that the shape of the transformer and fins play an important role in thermal performance of such systems.

Study of winding vibration and transmission characteristics of three-phase oil-immersed distribution transformer based on FEA

In this paper, the magnetic-structure-acoustic multi-physical field model of S13-M400/10 distribution transformer is established through the FEA software. The harmonic response analysis method is used to study the winding vibration and transmission characteristics of the transformer. The simulation results show that the flux leakage distribution of windings on each core column is mainly determined by the current flowing through these windings. The radial and axial acceleration distributions of the windings are U shape and M shape respectively along the winding height. The acceleration of B phase windings is smaller than that of A and C phase windings. The vibration of the oil tank surface is concentrated in its middle and lower part. The tank side vibration is mainly affected by the vibration of the nearest phase windings, while the tank front vibration is affected by the vibration of the three-phase windings together. This study is of great significance for further studies of the vibration characteristics of the transformer under unbalanced load and proposing the vibration reduction and noise reduction measures for the distribution transformer.

Deep Reinforcement Learning-Based Voltage Control to Deal with Model Uncertainties in Distribution Networks

This paper addresses the voltage control problem in medium-voltage distribution networks. The objective is to cost-efficiently maintain the voltage profile within a safe range, in presence of uncertainties in both the future working conditions, as well as the physical parameters of the system. Indeed, the voltage profile depends not only on the fluctuating renewable-based power generation and load demand, but also on the physical parameters of the system components. In reality, the characteristics of loads, lines and transformers are subject to complex and dynamic dependencies, which are difficult to model. In such a context, the quality of the control strategy depends on the accuracy of the power flow representation, which requires to capture the non-linear behavior of the power network. Relying on the detailed analytical models (which are still subject to uncertainties) introduces a high computational power that does not comply with the real-time constraint of the voltage control task. To address this issue, while avoiding arbitrary modeling approximations, we leverage a deep reinforcement learning model to ensure an autonomous grid operational control. Outcomes show that the proposed model-free approach offers a promising alternative to find a compromise between calculation time, conservativeness and economic performance.

Research on the temperature rise characteristics of power transformers based on fluid-solid-thermal coupling

The problems of overheating and insulation are the main influencing factors to the operation status of power transformers. Based on the physical model of a 50MVA/110kV oil-immersed self-cooling transformer, the electromagnetic, temperature and fluid field are introduced to establish a three-dimensional temperature rise model of the transformer in this thesis. The loss obtained from the electromagnetic field calculation model is taken as a heat source and input into the transformer temperature rise model. The results show that the hot spot temperature occurs in the core column and increases with the maximum load current when the single-phase ground fault occurs, and the hot spot temperature in the transformer exceeds the limit value. The temperature distribution trends of the core and high and low voltage windings under rated conditions and overload conditions are similar. In addition, the average temperature rise of the windings under overload conditions exceeds the limit value.

Test and Experimental Study on Vibration and Noise Characteristics of Distribution Transformer

With the continuous scale expansion of power grid, more and more distribution transformers go deep into the urban residential center, which results in increasingly prominent vibration and noise problems. Mastery of the vibration and noise characteristics of the distribution transformer and its propagation law is an important test basis for proposing vibration and noise reduction measures. Relying on a typical 10 kV distribution transformer, vibration and noise tests were carried out on the interior and exterior of transformer tank respectively in this paper. Advanced fiber-optic hydrophone test system was adopted in the test to solve the problem of accurately measuring the internal sound pressure of the transformer in a high electromagnetic field. Finally, time-domain analysis and frequency-domain analysis were done on test data to acquire the acoustic-vibration characteristic and propagation law of the 10 kV distribution transformer. The vibration spectrum of a transformer body is mainly 100 Hz and its rate, the vibration characteristics of distribution transformer tank is basically consistent with the internal transformer core, and the propagation of transformer vibration and noise in oil shows obvious laws.