Guillermo Aponte Mayor

Current Status and Future Trends in Frequency-Response Analysis With a Transformer in Service

This paper presents the current status and future trends in the application of the frequency-response analysis (FRA) technique with the transformer in service (online) through bibliographic review and analysis. As a result, three basic stages of the online FRA test have been identified and defined: injection and excitation signal measurement; recording, filtering and processing of measured signals; and curve analysis and interpretation. This work presents an overview of the online FRA technique, useful for subsequent research in this area.

Detection of Transformer Faults Using Frequency-Response Traces in the Low-Frequency Bandwidth

This paper describes a new procedure which facilitates the frequency-response curve interpretation in the low-frequency bandwidth. The procedure is able to estimate the magnetization inductance and winding capacitance, for each transformer phase by only using data from its frequency response. The described calculation procedure uses an R-L-C electrical equivalent circuit developed to simulate the impedance measured in the frequency-response test. The procedure takes into account the magnetic coupling among different phases and allows their analysis separately, enabling the identification of a possible failure. This paper describes the procedure to obtain the parameters and its application for interpreting the low-frequency results of frequency-response analysis measurement cases.

Application of Wavelet Transform to Obtain the Frequency Response of a Transformer From Transient Signals—Part II: Practical Assessment and Validation

This paper presents a practical assessment and validation for the new proposed approach based on the continuous wavelet transform (CWT) to obtain the frequency response from online transient signals for an actual transformer. Apart from the mathematical procedure, an electronic system was also designed and implemented in order to inject superimposed controlled pulses to the power system (50/60 Hz) wave. The results show improved performance of the wavelet transform compared to the Fourier transform, for transient signal analysis to be applied on a nonintrusive transformer monitoring approach. Particularly, this new approach enables overcoming some problems related to the signal filtering and the signal processing in an online frequency-response analysis transformer diagnosis. This paper is presented in three parts. Part I showed the main theoretical basis of this approach. The current Part II shows a practical assessment based on tests performed in a three-phase transformer of 1150/345 V-5 kVA and in a single-phase transformer of 13200/240 V-15 kVA. Part III shows the performance of this new approach on transformers being diagnosed under real conditions.

Ozonización del agua de piscinas: una alternativa al método tradicional de cloración

Resumen es: Tradicionalmente se ha utilizado la cloracion en el tratamiento del agua de piscina, sin embargo, debido a los problemas asociados a su uso, actualmente ...

Experimental Results of a Cost-Effective Ozone Generator for Water Treatment in Colombia

Obtaining high-quality cost-effective water, minimizing the public health risk generated by pathogenic elements or disinfection sub-products such as trihalomethane and/or chlorophenol, has made necessary the use of technologies different to chlorination. In this paper, we present the implementation of a high-voltage, high-frequency flyback inverter to generate ozone, and outline the main characteristics and uses of a prototype of water ozonation from a well for a hospital in Colombia. With the prototype, the ozone dose can be adjusted through the duty cycle modulation; switching was done with a Mosfet and the voltage signal was increased with a ferrite technology transformer. The source is characterized by its simplicity, good performance and low cost.

Non-minimum Phase Effects in Transformer Low-Frequency Bandwidth Responses

This paper presents the analysis and modeling of the non-minimum phase effects that can occur in the low-frequency response of transformers. This effect is highlighted when the phase response has angles outside the range –90° to +90° and the typical response shape, which consists of two resonance points for the lateral phases and one for the central phase, is not found. Analysis based on physical effects, particularly the grounding capacitances and their association with the response, is presented. A model is proposed for characterizing and reproducing transformer low-frequency response, including the non-minimum phase effect. Actual frequency response measurements were obtained experimentally to assess the modeling.