Desarrollo, diseño e implementación de un equipo para detección preventiva del estado de aisladores tipo cadena para aplicaciones de alta tensión.
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Date
2024
Journal Title
Journal ISSN
Volume Title
Publisher
Universidad de Concepción
Abstract
El problema de conocer el nivel de contaminación sobre la superficie de los aisladores en instalaciones de alta tensión es de vital importancia, ya que la programación de los lavados es realizada principalmente en base a la experiencia, lo que no asegura que el sistema eléctrico esté libre de fallas ni tampoco de que la frecuencia de los lavados se realice de manera eficiente desde un punto de vista de costos. Aunque existen diversas soluciones para determinar el nivel de la contaminación en aisladores, la que parece ser la más recurrente es el análisis de la corriente de fuga. El aumento de la amplitud y de la distorsión de la corriente que circula por el aislador presenta una relación directa con el aumento de la contaminación y la humedad.
Por otro lado, la literatura presenta una serie de índices basados en la corriente de fuga como el valor efectivo, peak, THD y relaciones entre armónicos; que buscan determinar el nivel de contaminación sobre la superficie de los aisladores. En general, el resultado de los índices y su desempeño depende de diferentes variables como la humedad y la contaminación, pero también del tiempo de aplicación de la humedad y variables externas, por lo que es muy relevante el instante en el que se realiza la medición de corriente de fuga y el cálculo de estos índices. En aplicaciones industriales la humedad varía considerablemente y las mediciones de corriente de fuga pueden no ser continuas en el tiempo.
Por otra parte, para medir la corriente de fuga en cadenas de aisladores la literatura muestra diferentes soluciones principalmente orientadas a aplicaciones en laboratorio, la mayoría de tipo invasivo por lo que no son soluciones reales que sean atractivas para implementar en la industria. Este trabajo presenta el desarrollo, diseño e implementación de un sistema para determinar el nivel de contaminación en aisladores tipo cadena. El sistema propuesto consta de un sensor de corriente de fuga tipo tenaza con núcleo de material ferromagnético abierto capaz de medir corrientes de fuga de baja amplitud, que no afecta la distancia de fuga de la cadena de aisladores y tampoco afecta la aislación al ser no invasivo. Este sensor es probado en laboratorio, también en un aislador dentro de una cámara de niebla artificial y en una subestación de alta tensión. Los resultados muestran que el sensor mide correctamente corrientes de fuga mostrando amplitudes del orden de los miliamperes y una relación directa con la humedad registrada. La tesis incluye un análisis detallado del efecto de la humedad y la contaminación en índices presentados en la literatura para determinar el nivel de contaminación sobre la superficie de los aisladores. El análisis de los parámetros de la corriente de fuga se realiza en función del tiempo y se destaca la importancia del tiempo de exposición
de la capa de contaminación de la superficie a la humedad. También, se introduce el concepto de impedancia armónica en aisladores, con tal de observar la evolución de la magnitud en el tiempo donde se destaca que algunos armónicos de la corriente de fuga son propios del efecto de la humedad y la contaminación en el aislador como otros que dependen de variables externas como el voltaje de la red. Finalmente, este trabajo muestra el resultado de la medición de variables ambientales y de corriente de fuga por medio del sistema diseñado en una subestación de 220 kV y en 4 puntos de medición en distintas líneas de alta tensión de 220 y 500 kV en el norte de Chile.
La principal contribución de este trabajo se centra en el diseño e implantación de un sensor de corrientes de fuga no invasivo, para aplicaciones en aisladores tipo cadena, y de un procedimiento de análisis detallado del comportamiento de la corriente de fuga que sirve para determinar el nivel de contaminación, lo que permite definir procedimientos de mantenimiento adecuados.
The problem of knowing the level of contamination on the surface of high voltage insulators is critical. Washing scheduling is mainly done on the basis of experience, which does not ensure that the electrical systems are free of faults or that the frequency of washing is cost-efficient. Although there are various solutions for determining the level of contamination in insulators, leakage current analysis is the most commonly used method. The increase in amplitude and distortion of the current flowing through the insulator is directly related to the increase in contamination and humidity. On the other hand, the literature presents a series of indices based on the leakage current, such as RMS, peak, THD and harmonic ratios, which attempt to determine the level of contamination on the surface of the insulators. In general, the result of the indices and their performance depend on different variables such as humidity and contamination, but also on the time of application of the humidity and external variables, so the time at which the leakage current measurement and the calculation of these indices are performed is very relevant. In industrial applications, humidity varies considerably and leakage current measurements may not be continuous over time. On the other hand, to measure the leakage current in insulator strings, the literature shows different solutions mainly oriented to laboratory applications, most of them invasive, so they are not real solutions that are attractive to implement in the industry. This work presents the development, design and implementation of a system to determine the level of contamination in string insulators. The proposed system consists of a clamp-type leakage current sensor with an air gap ferromagnetic core that is capable of measuring low amplitude leakage currents that do not affect the leakage distance of the insulator string and do not affect the insulation since it is non-invasive. This sensor is tested in the laboratory, including on an insulator in an artificial fog chamber and in a high-voltage substation. The results show that the sensor correctly measures leakage currents with amplitudes in the order of milliamperes and a direct relationship to the recorded humidity. The thesis includes a detailed analysis of the effect of humidity and contamination on the indices presented in the literature to determine the level of contamination on the surface of the insulators. The analysis of the leakage current parameters as a function of time is performed and the importance of the exposure time of the surface contamination layer to moisture is highlighted. Also, the concept of harmonic impedance on insulators is introduced in order to observe the evolution of the magnitude over time, where it is highlighted that some harmonics of the leakage current are due to the effect of moisture and contamination on the insulator, as well as others that depend on external variables such as the mains voltage. Finally, this work shows the result of the measurement of environmental variables and leakage current by means of the system designed in a 220 kV substation and in 4 measuring points in different high voltage lines of 220 and 500 kV in the north of Chile. The main contribution of this work focuses on the design and implementation of a non-invasive leakage current sensor for applications in string-type insulators and a detailed analysis procedure of the leakage current behavior to determine the level of contamination, which allows the definition of appropriate maintenance procedures.
The problem of knowing the level of contamination on the surface of high voltage insulators is critical. Washing scheduling is mainly done on the basis of experience, which does not ensure that the electrical systems are free of faults or that the frequency of washing is cost-efficient. Although there are various solutions for determining the level of contamination in insulators, leakage current analysis is the most commonly used method. The increase in amplitude and distortion of the current flowing through the insulator is directly related to the increase in contamination and humidity. On the other hand, the literature presents a series of indices based on the leakage current, such as RMS, peak, THD and harmonic ratios, which attempt to determine the level of contamination on the surface of the insulators. In general, the result of the indices and their performance depend on different variables such as humidity and contamination, but also on the time of application of the humidity and external variables, so the time at which the leakage current measurement and the calculation of these indices are performed is very relevant. In industrial applications, humidity varies considerably and leakage current measurements may not be continuous over time. On the other hand, to measure the leakage current in insulator strings, the literature shows different solutions mainly oriented to laboratory applications, most of them invasive, so they are not real solutions that are attractive to implement in the industry. This work presents the development, design and implementation of a system to determine the level of contamination in string insulators. The proposed system consists of a clamp-type leakage current sensor with an air gap ferromagnetic core that is capable of measuring low amplitude leakage currents that do not affect the leakage distance of the insulator string and do not affect the insulation since it is non-invasive. This sensor is tested in the laboratory, including on an insulator in an artificial fog chamber and in a high-voltage substation. The results show that the sensor correctly measures leakage currents with amplitudes in the order of milliamperes and a direct relationship to the recorded humidity. The thesis includes a detailed analysis of the effect of humidity and contamination on the indices presented in the literature to determine the level of contamination on the surface of the insulators. The analysis of the leakage current parameters as a function of time is performed and the importance of the exposure time of the surface contamination layer to moisture is highlighted. Also, the concept of harmonic impedance on insulators is introduced in order to observe the evolution of the magnitude over time, where it is highlighted that some harmonics of the leakage current are due to the effect of moisture and contamination on the insulator, as well as others that depend on external variables such as the mains voltage. Finally, this work shows the result of the measurement of environmental variables and leakage current by means of the system designed in a 220 kV substation and in 4 measuring points in different high voltage lines of 220 and 500 kV in the north of Chile. The main contribution of this work focuses on the design and implementation of a non-invasive leakage current sensor for applications in string-type insulators and a detailed analysis procedure of the leakage current behavior to determine the level of contamination, which allows the definition of appropriate maintenance procedures.
Description
Tesis presentada para optar al grado de Doctor en Ciencias de la Ingeniería con mención en Ingeniería Eléctrica
Keywords
Aisladores eléctricos, Alto voltaje, Sistemas eléctricos de potencia