Publication: Análisis del envejecimiento del aceite de un transformador mediante espectroscopía dieléctrica medida en baja frecuencia
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2009
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2009-12-22
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Abstract
El transformador de potencia es una máquina eléctrica capaz de transformar una energía eléctrica de entrada con determinadas magnitudes de tensión y corriente en otra energía eléctrica de salida con magnitudes diferentes. Hoy en día no se concibe el poder vivir sin el uso de la electricidad y por tanto sin el uso de estos transformadores que nos facilitan tanto el transporte como el suministro eléctrico, de ahí viene la importancia de su estudio, del análisis y mejora de sus fallos para un uso más eficiente del mismo pudiendo alargar la vida útil del mismo. Esta duración de vida está directamente relacionada con la vida del papel y cartón aislante y del aceite dieléctrico, los tres componentes más importantes sujetos a la deteriorización y la contaminación. Este proyecto se detiene en el estudio del envejecimiento del aceite mineral aislante de los transformadores de potencia, el cual nos muestra valiosa información sobre las condiciones de operación de los equipos que los usan. Estos aceites son productos que sufren degradación por los esfuerzos térmicos y eléctricos a los que están continuamente sometidos, generando productos de descomposición que son utilizados para evaluar la presencia de un problema o falla en los transformadores. Una de las magnitudes utilizadas para comprobar el envejecimiento del aceite es la permitividad dieléctrica en función de la frecuencia. En medios no magnéticos, nos informa totalmente de su respuesta electromagnética. La espectroscopía dieléctrica permite conocer parámetros fundamentales desde el punto de vista de la investigación científica básica y desde un punto de vista tecnológico, conocer la respuesta del material a cualquier señal electromagnética. El objetivo de este trabajo es la caracterización de pequeñas muestras mediante espectroscopía en el dominio de la frecuencia (Frequency Domain Spectroscopy o FDS) calculando la permitividad dieléctrica compleja en baja frecuencia, en el rango de 1mHz a 1KHz. A su vez, estas medidas han sido realizadas a dos niveles de tensión, de 5V y 140V para poder tener más pruebas que certifiquen el diferente grado de envejecimiento según la tensión aplicada desde el punto de vista de la medición. Tanto el fondo teórico como la metodología utilizada o los procedimientos de análisis y los resultados obtenidos son posteriormente explicados, más ampliamente y con detenimiento, en los siguiente capítulos de este libro. Este proyecto ha estado limitado por el número de muestras ensayadas, ya que habría sido interesante haber realizado los ensayos a una mayor cantidad de muestras con el fin de dar una mayor validez estadística. ______________________________________________________________________________________
The power transformer is an electrical device that transforms an input electrical energy with certain magnitudes of voltage and current into another output power with different magnitudes. Today living without using energy seems inconceivable. Transformers which provide both transport and electricy supply are therefore essential. Hence comes the importance of their study and, of the analysis and improvement of their failures to reach a more efficient use which may extend their useful life. This life expectancy is directly related to the life expectancies of the three most important components of a power transformer, the paper, the cardboard and the oil dielectric insulation which are subjected to deterioration and pollution. In this project we focus on the study of aging of insulating oil for power transformers, which shows us valuable information about how the operators use them. These oils are continually subjected to electrical and thermal stresses which deteriorate them. The breakdown products generated by the damage are used to assess the presence of a problem or a fault in the transformer. A way to measure the oil aging is to use the evolution of the permittivity with the frequency. In a nonmagnetic environment it gives the complete electromagnetic response of the oil. With a dielectric spectroscopy it is possible to know fundamental parameters from a basic scientific research standpoint, and from a technological standpoint it is possible to know the material response to any electromagnetic signal. The aim of this paper is the characterization of small samples by Frequency Domain Spectroscopy or FDS, calculating the complex dielectric permittivity at low frequency, with a range of 1MHz to 1 kHz. Then these measures have been undertaken at two levels of voltage, 5V and 140V in order to have more tests to certify the different level of aging as the applied voltage. The theoretical background and the methodology used, or the analysis methods and its results are subsequently explained with more details in the following chapters of this book. This project has been limited by the number of samples tested; however it would have been interesting to carry out the tests to a larger number of samples in order to give greater statistical validity.
The power transformer is an electrical device that transforms an input electrical energy with certain magnitudes of voltage and current into another output power with different magnitudes. Today living without using energy seems inconceivable. Transformers which provide both transport and electricy supply are therefore essential. Hence comes the importance of their study and, of the analysis and improvement of their failures to reach a more efficient use which may extend their useful life. This life expectancy is directly related to the life expectancies of the three most important components of a power transformer, the paper, the cardboard and the oil dielectric insulation which are subjected to deterioration and pollution. In this project we focus on the study of aging of insulating oil for power transformers, which shows us valuable information about how the operators use them. These oils are continually subjected to electrical and thermal stresses which deteriorate them. The breakdown products generated by the damage are used to assess the presence of a problem or a fault in the transformer. A way to measure the oil aging is to use the evolution of the permittivity with the frequency. In a nonmagnetic environment it gives the complete electromagnetic response of the oil. With a dielectric spectroscopy it is possible to know fundamental parameters from a basic scientific research standpoint, and from a technological standpoint it is possible to know the material response to any electromagnetic signal. The aim of this paper is the characterization of small samples by Frequency Domain Spectroscopy or FDS, calculating the complex dielectric permittivity at low frequency, with a range of 1MHz to 1 kHz. Then these measures have been undertaken at two levels of voltage, 5V and 140V in order to have more tests to certify the different level of aging as the applied voltage. The theoretical background and the methodology used, or the analysis methods and its results are subsequently explained with more details in the following chapters of this book. This project has been limited by the number of samples tested; however it would have been interesting to carry out the tests to a larger number of samples in order to give greater statistical validity.
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Keywords
Transformadores eléctricos, Aislantes eléctricos, Espectroscopía dieléctrica