Performance Of Power Transformers Research Articles

Probabilistic Analysis of the Reliability Performance for Power Transformers in Egypt

From reliability, maintainability, and availability (RAM) points of view, the performance of power transformers has a significant impacts on the performance of the entire power network. Their performance has also a significant impacts on the power interruptions at various voltage levels and the consequent customer interruption costs. This paper will discuss the estimated remaining lifetime of power transformers in the voltages subpopulations: 500kV, 220 kV, 132 kV, 66kV and 33 kV of the Egyptian grid as time between failures (TBFs) will be determined and then determine the best fit probability distribution using MATLAB program for repair time, customer interruption costs (CIC) and TBFs, this is performed in order to estimate remaining lifetime of the transformers, from which the best fit probability distribution will be used in this case study which is Weibull distribution. Finally availability of the transformers per different voltage populations is calculated and determined. Different subassemblies (failures) are also undergo the same process of determining TBFs and estimating remaining lifetime. The results will be helpful in the manufacturing process of the transformers and enhancing the maintenance schedule.

Heat transfer enhancement from power transformer immersed in oil by earth air heat exchanger

In this study, the modelling of power transformer with (250 kVA) by using (ANSYS17.1/FLUENT) code program was done. The power transformer was connected with earth air heat exchanger to decrease the temperature of (oil, core, and coils) of transformer which will increase its efficiency for preventing the damage and/or failure. The case study used the weather conditions of Nasiriya city, Iraq, at July 1st with 50?C as maximum ambient temperature and full electrical load of the power transformer. In addition to different pipe diameter, length of earth air heat exchanger and different air velocity entering to pipe. The results showed the temperature of (oil, core, and coils) for power transformer decreased with increase the pipe length and earth air heat exchanger depth underground. The air velocities inlet to earth air heat exchanger that used in the study were (2, 4 , and 6 m/s, respectively) and the results showed the increasing of air velocity inlet to earth air heat exchanger should decrease the temperature of (oil, core, and coils) for power transformer and increase the thermal conductivity of oil. The study concluded when using earth air heat exchanger in the power transformer and performance of power transformer will be increasing and led to decrease the temperature of oil about (18.5?C).The results showed a significant convergence with previous researches.

Transformadores de distribución que operan con aceite de origen vegetal como dieléctrico y refrigerante

Researches related with the use of Natural Ester Fluids as refrigerant of power transformers have been developed in other countries with successful results. In Colombia there is no a procedure to control the use of these esters in electrical apparatus, so the current implementations are regulated by NTC 1465 standards for mineral esters. This new proposal involves the composition and the most relevant properties (the ignition resistance, impact on the lifetime of the insulating papers and the impact on the environment), which makes the application of natural esters fluids advantageous not only to preserve the environment but also to get a better performance of power transformers.

Challenges in calibration of the measurement of partial discharges at ultrahigh frequencies in power transformers

The detection and measurement of partial discharge (PD) is a well-known method for evaluating the insulation performance of power transformers. According to the IEC 60270 standard, the apparent charge is measured in a frequency range below 1 MHz using an electrical circuit which quantifies only a portion of the discharge energy conducted to the PD detector through the conductors. However, it is also well known that the PD energy is not only conducted but also transmitted via electromagnetic (EM) and optic waves, acoustic waves, and thermal energy.

Effect of Ambient Conditions on Performance of Power Transformers

Effect of Ambient Conditions on Performance of Power Transformers

Performance Analysis and Optimisation of an Oil Natural Air Natural Power Transformer Radiator

In Power transformers are inevitable components in alternating current generation, transmission, distribution and utilization systems. Lifespan and performance of power transformer are dependent on cooling system employed for dissipation of heat generated during its operation. In this paper numerical simulation of an oil natural air natural power transformer radiator was performed to determine its cooling capacity. In addition, optimum spacing between sections and optimum length of sections of radiator were also determined. An optimised radiator design was proposed and was simulated to determine its cooling capacity. The proposed radiator design was found to 14% more efficient than existing design in terms of cooling capacity for same material cost. The control volume method has been used to resolve the continuity, the momentum and the energy equations in steady state.

Reducing Environmental Impact and Improving Safety and Performance of Power Transformers With Natural Ester Dielectric Insulating Fluids

Natural ester fluids may be used in new transformers as well as to retrofill existing units in order to improve their performance and reliability. Designing or retrofilling power transformers with natural ester fluids requires, however, to account for a number of significant differences in properties, characteristics, and material parameters between natural ester fluids and mineral oil in order to obtain the desired performance (thermally and dielectrically). This paper gives a comprehensive review of natural-ester-fluid main properties and associated values when it comes to environmental impact, fire resistance, and overall performance of transformers filled with such fluids. The key fluid characteristics impacting the design of power transformers are also highlighted.

A Realistic Method for Remaining Service Life Prediction of Power Transformer

In recent years, many studies have been done on monitoring, analyzing and aging performance of power transformer which is one of the most important components of power system. It is important to know the loading capacitance and remaining service life of a transformer to ensure its economical and secured operation. In this study, a realistic method is presented for remaining service life prediction and life-loss calculation of the power transformers. The proposed method is applicable for all the power transformers and can be updated in the light of the relevant standards for the different liquid and solid insulation materials. As a case study, life-loss calculation and the remaining service life prediction is carried out using thermal model that has been created considering the parameters of the 250 MVA mineral oil–immersed power transformer

Virtual valuations [transformer testing

Modern power transformers are tightly designed to minimise volume, weight and cost. One solution to striking this delicate balance is to test the transformer in a virtual way at the design stage, through numerical simulation. When power transformers fail to meet their specification, it is almost always due to a very localised effect. such as a hot spot on the tank wall or an insulation breakdown at a critical point in the winding. Finite element methods are ideally suited to calculating local electric and magnetic field variations and, for more than 30 years, have been used for examining the performance of power transformers.

The transformer short-circuit test and the high power laboratory in China the past, present, and future

Over the last half-century, the transformer industry in China has experienced substantial development due to the study of the short-circuit performance of power transformers by using short-circuit tests. This is because power transformers operating in power systems are exposed to short circuits, which cause high short-circuit currents of more than 10 times the rated current and are dangerous to the transformer. In this paper, the author reviews short-circuit testing of distribution transformer, including power transformers. The Hushita I High Power Test Laboratory is also described in this paper along with its main equipment and test capabilities. Potential for future development is also discussed.

Neural networks for the prediction of magnetic transformer core characteristics

Because the performance of power transformers is by various distinct parameters of the magnetic core, the prediction of relevant characteristics such as no-load losses P by analytical methods is impractical. This paper reports first attempts to predict the dependence of P on several parameters of core design by means of artificial neural networks (ANN's). Investigations of several ANN versions showed good results for simple backpropagation networks equipped with several output neurons for an adaptive version of Gaussian coarse coding. A main problem arises from the fact that an increase of input parameters is linked with a large increase in training batches established by time-consuming model core experiments. As a compromise, first ANN's were trained for the prediction of the losses P/sub J/ of "linearized" joint regions as a function of the most relevant parameters, including the number of overlap steps and the mean air-gap length of joints. This yields rough estimations of the joint's contribution to the building factor for small cores. For larger cores, an ANN cascade structure was tested. It includes a second ANN that considers indirect effect of joint designs on the global distribution of losses. The major problem with an ANN-based prediction system is establishing representative training data. Modified versions of the ANN method can be applied to various tasks, including the prediction of losses and noises of full-sized cores.