A Bibliographic Analysis of Transformer Literature 1990-2000 (original) (raw)

A Bibliographic Analysis of Transformer Literature 2001-2010

8th Mediterranean Conference on Power Generation, Transmission, Distribution and Energy Conversion (MEDPOWER), 2012

This paper analyzes the bibliography on transformer research covering the period of 2001-2010. Due to the large number of publications in peer review journals, conferences and symposia contributions were not included. That is why 22 peer review journals were investigated, in which 933 papers including the word “transformer” in their title have been published in the decade 2001-2010. The most productive and high-impact authors and countries are identified. The four most productive countries are Japan, USA, China, and Canada. More than 75 citations were received by each one of the five most cited papers. The bibliographic research presented in this paper is important because it includes and analyzes the best research papers on transformers coming from many countries all over the world and published in top rated scientific electrical engineering journals.

Modeling and Analysis of Transformer

The transformers are an integral part of the power system. In transformers, the main consequence of harmonic currents is an increase in losses, mainly in windings, because of the deformation of the leakage fields. Higher losses mean that more heat is generated in the transformer so that the operating temperature increases, leading to deterioration of the insulation and a potential reduction in lifetime. Due to the non-linear loads, the transformers are much affected by the distorted currents and supply voltages which largely reduce its efficiency due to overheating. Nonlinear loads cause harmonics to flow in the power lines which can overload wiring and many desktops, personal computers present nonlinear loads to the AC supply because of their power supplies design (capacitor input power supply). In power transformers, the main consequence of harmonic currents is an increase in losses, mainly in windings, because of the deformation of the leakage fields. Higher losses mean that more heat is generated in the transformer so that the operating temperature increases, leading to deterioration of the insulation and a potential reduction in lifetime. As a result, it is necessary to reduce the maximum power load on the transformer, a practice referred to as de-rating, or to take extra care in the design of the transformer to reduce these losses. To estimate the de-rating of the transformer, the load's K Factor may be used. Thus analysing this problem and reducing the losses of the transformer has become a major area of research in today's scenario. This report includes the effects of non-sinusoidal supply voltage on the transformer excitation current and the core losses which includes eddy current and hysteresis losses. INTRODUCTION Events over the last several years have focused attention on certain types of loads on the electrical system that results in power quality problems for the user and utility alike. Equipment which has become common place in most facilities including computer power supplies, solid state lighting ballasts, adjustable speed drives (ASDs), and uninterruptible power supplies (UPSs) are examples of non-linear loads. It is forecast that before the end of the century, half of all electrical devices will operate with a nonlinear current draw. These nonlinear loads are the cause of current harmonics. Non-linear loads are loads in which the current waveform does not have a linear relationship with the voltage waveform. Non-linear loads generate voltage and current harmonics which can have adverse effects on equipment that are used to deliver electrical energy such as transformers, feeders, circuit breakers, which are subjected to higher heating losses due to harmonic currents consumed by non-linear loads. The discontinuous, Harmonic currents cause overheating of electrical distribution system wiring, transformer overheating and shortened transformer service life. Electrical fires resulting from distribution system wiring and transformer overheating were rare occurrences until harmonic currents became a problem. Transformers which provide power into an industrial environment are subject to higher heating losses due to harmonic generating sources (non-linear loads) to which they are connected. The major source of harmonic currents is the switch mode power supply found in most desktop computers, terminals, data processors and other office equipment is a good example of a non-linear load. The switching action of the computer power supply results in distortion of the current waveform [2]. Harmonics are produced by the diode-capacitor input section of power supplies. The diode-capacitor section rectifies the AC input power into the DC voltage used by the internal circuits. The personal computer uses DC voltage internally to power the various circuits and boards that make up the computer. The circuit of the power supply only draws current from the AC line during the peaks of the voltage waveform, thereby charging a capacitor to the Peak of the line voltage. The DC equipment requirements are fed from this capacitor and, as a result, the current waveform becomes distorted. The increasing usage of non-linear loads on electrical power systems is causing greater concern for the possible loss of transformer life. So, Manufacturers of distribution transformers have developed a rating system called K Factor, a design which is capable of withstanding the effects of harmonic load currents. The amount of harmonics produced by a given load is represented by the term "K" factor. The larger the "K" factor, the more harmonics are present [3].

Review On Investigating The Failure Of Power Transformer And Its Mitigating Strategies

Journal of emerging technologies and innovative research, 2020

One of the most relevant electrical energy transfer components in the power system industry is the power transformer. The reliability and security of the safety of the power transformer is paramount for system operation and controls. Ageing, overvoltages, over fluxing and the occurrence of prevailing faults in the power transformer needs critical attention to prevent the power transformer's poor efficiency, failure and explosion. The various mitigation techniques for tackling those power quality issues are also considered and discussed in this paper.