ResumenEste artículo presenta la implementación de un modelo para el análisis del comportamiento en frecuencia de los parámetros de un transformador eléctrico. El modelo se obtiene a partir de la curva de la prueba de Respuesta en Frecuencia del transformador (FRA). Esta prueba consiste básicamente en obtener una característica del transformador y comparar el resultado con una referencia del mismo, tomada anteriormente y considerada como normal. Las diferencias pueden indicar algún tipo de daño en el transformador. Se hace la descripción del modelo, de la manera como se realizó su implementación, del procedimiento para obtener sus parámetros y de su aplicación en el análisis de variaciones en las curvas obtenidas en los ensayos de FRA. Este modelo es una herramienta que puede emplearse como ayuda para identificar problemas de tipo mecánico en el transformador. Palabras clave: transformador, parámetros del transformador, respuesta en frecuencia, FRA Implementation of an Electric Transformer Model for its Frequency Response Analysis AbstractThis article presents the implementation of a model for the analysis of the frequency behavior of a transformer. The model is obtained from the Frequency Response Test (FRA). This test consists basically of obtaining the characteristics of the transformer and comparing the results with those of a reference transformer, which are previously known and considered as normal-The differences indicate that the transformer has certain damage. The article describes the model, its implementation, the procedure to obtain its parameters and its application in the analysis of the curve variations obtained by the FRA tests. This model represents a good tool that can be used as support to identify some type of mechanical problem in the transformer.

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This paper describes a new procedure to estimate separately the magnetization inductance Lm and winding shunt capacitance Cm for each power transformers phase, using and R-L-C electrical equivalent circuit developed to simulate the impedance measured in the Frequency Response Test. The Lm and Cm parameters can be used to analyze the traces obtained in the test. It is also shown experimental results that demonstrate the procedure ability to interpret the FRA traces providing an added value to the graphical comparison. This procedure has a direct application in the FRA based diagnosis because allows failure detection using reliable parameters when the magnetic field of the core is involved.

Transformer monitoring based on the operating condition (on-line test) has boomed in recent years because it allows early detection of risk situations or limitations regarding use to make appropriate decisions before a failure occurs. Frequency response analysis (FRA) is one of the most heavily researched techniques for on-line development; it is based on obtaining a transformer's frequency response (admittance, impedance or transfer function) in a given bandwidth. This paper presents an experimental method for obtaining the frequency response with the transformer in service by injecting controlled pulses of the voltage signal using an external electronic circuit. Once the voltage and current signals had been recorded, the wavelet transform was used via multi-resolution analysis (MRA) for filtering. This led to results being obtained without noise interference from the electrical system. The transfer function was obtained in terms of impedance, using the fast Fourier transform (FFT). The proposed method represented an alternative in solving some problems arising from the on-line FRA technique such as filtering and results' repeatability. The tests involved a 5-kVA 1150/345 V three-phase transformer and a 3-kVA, 7620/240 V single-phase transformer in the Universidad del Valle's High Voltage Laboratory.

Este artículo describe un algoritmo novedoso para la estimación de la inductancia de magnetización y la capacitanciadel devanado de cada fase del transformador, a partir de los datos de la curva de respuesta en frecuencia, utilizando unmodelo del núcleo del transformador. El uso del modelo aplicado a las tres medidas de cada fase del transformadorpermite localizar y cuantificar una posible falla en baja frecuencia sin necesidad de disponer de las medidas FRAde referencia. Se hace la descripción del modelo, del algoritmo para obtener los parámetros de cada fase y de suaplicación en la interpretación de las variaciones en bajas frecuencias de la curva FRA, finalmente se muestran doscasos de aplicación.