Characterization of Peltier cells for energy harvesting applications (I)

Módulo Peltier, 32.8W, 6A, 8.8VPeltier cells are usually applied to cool surfaces when connected to an electric power supply but they can also convert differences of temperature between their sides into a voltage, known as the Seebeck effect. Therefore, it is possible to have a voltage at the ends of the wires of a Peltier cell by applying heat to one of the sides and attaching a heatsink to the other side. In terms of energy harvesting, the heat should come from a residual source such as an electrical or mechanical machine or, simply, the sun using Fresnel lenses. The cooling of the other side should be passive to minimize the energy consumption, hence the use of a heatsink. It is important to know how much energy can be obtained with a single cell as a function of the difference of temperatures, for this reason, the characterization of the cell must be the first step in the design of applications scavenging energy.

20170324_162157.jpgThe mounting scheme is shown in the side Figure where the heatsink is clearly seen on top of the cell. This is hidden by some pieces of thermal insulating foam but the two wires are visible. Finally, an aluminium plate has been adhered to the cell with a thermal conductive bonding paste.

The aim of this work is to obtain the Thévenin equivalent of an Adaptive ETH-071-14-15 Peltier cell but the process is valid for any other type of cell. The datasheet details the working curves when the cell is used as load but nothing is said about its characteristics when used as a source. The characterization requires the application of a known difference of temperatures, ΔT, and this is achieved injecting current to a pair of ceramic resistors  of 47 Ω in parallel attached to the aluminium plate with silicone.

20170324_162012

20170324_161932_001Two LM35 temperature sensors read the temperature of the aluminium plate and the heatsink. Notice that, once the plate and the heatsink are attached to the cell, its sides are no longer reachable so the sensors have to be connected to the closest surfaces to the cell. There will be an uncertainty in the measurements but we can asume that it is negligible or, at least, that it affects the two sensors in the same manner so the difference of temperatures is the same as in the surfaces of the cell. The mounted cell is enclosed in methacrylate box coated with thermal insulating panels ensuring that, once a constant difference of temperatures, ΔT, is achieved, it is maintained along the experiment so the output voltage can be directly related to the selected ΔT.

Next: Measurements.

Light source follower with Arduino

Autor: Bajo Sánchez, Cristina
Director: Robles Muñoz, Guillermo

 

Document in pdf (Spanish)

Video demonstration

Abstract – This work introduces the design of a light tracking system on two axes, based on the Arduino technology as analysis center and automated control of its peripherals. It mainly studies the way that the system operates and the achievement of reactions carried out by a set of devices when incident light is detected. It also analyses the peripheral components able to perform each of these functions and selects the most suitable ones among the different alternatives provided by the market place. This choice, together both the knowledge about the technical features and the possibility of being controlled and integrated in Arduino, takes a crutial role on the study and justification of the designed ensemble. This research process aims to incorporate the best components to the designed system in order to conduct each the proposed functions and, accordingly, the best features for a low-cost and dynamic nature prototype. Its multiple applications will make it a system that could meet many of the existing needs in the high-technology industries (energy, electronic, automation, home automation, etc.)

Keywords – light tracking, focal light, Arduino, photoresistor, servomotor, ultrasound sensor, LCD module.

Identificación de pulsos de descargas parciales en señales con ruido de conmutación

Autor: Martínez Merck, Beatriz
Director: Robles Muñoz, Guillermo

Documento en PDF

Resumen – Las descargas parciales son pequeñas rupturas dieléctricas que se producen en el interior de los sistemas de aislamiento de los distintos equipos eléctricos. Estas descargas son las responsables del deterioro progresivo del sistema y de la degradación total con el paso del tiempo. Mediante su estudio se puede detectar cuál es la fuente que puede producir fallos.
El estudio de descargas parciales en corriente alterna está muy avanzado. En cambio, hay muy pocas publicaciones que hagan referencia a las descargas parciales en corriente continua, a pesar de que este tipo de corriente sea muy utilizada en sistemas HVDC o en equipos electrónicos.
Hoy en día, el estudio de las descargas parciales en corriente continua es de vital importancia, puesto que, actualmente, se producen fallos en sistemas de este tipo que son difíciles de identificar. En equipos de aeronaves, por ejemplo, se ha detectado que el inicio de las descargas parciales se produce casi a tensión nominal, debido a las bajas presiones durante el vuelo.
En este trabajo se plantean distintas formas de identificar descargas parciales en corriente continua, mediante la obtención de patrones, que varían en función del origen de las descargas. Por lo tanto, a través de la comparación de patrones es posible separar distintos tipos de descargas parciales. Además, se presenta un experimento que demostrará la eficacia de los métodos de identificación propuestos.
También se presenta otra forma de separar pulsos, basada en la separación de espectros en frecuencia, ya que se ha demostrado que los espectros en frecuencia de los pulsos producidos por ruido de conmutación son distintos a los producidos por una descarga parcial. Este método consiste en la obtención de un mapa PRH-PRL que sirve para separar en función de dos intervalos de frecuencia (PRH y PRL) los pulsos de descargas parciales de los de conmutación.
El objetivo principal del trabajo es automatizar esta forma de identificar descargas parciales. Para ello se ha generado un código de análisis en Matlab a partir del cual se eligen, de entre todos los datos propuestos, los candidatos a ser una posible descarga parcial. La separación de los candidatos en pulsos de descargas parciales y en pulsos de conmutación se visualiza mediante el mapa PRH-PRL.
Con el fin de facilitar el análisis, se ha creado una interfaz en Guide, una herramienta de Matlab.

Keywords – HVDC, partial discharges, noise, clustering, identification.

Energy harvesting from partial discharges

Autor: Molina Sanz, Javier
Director: Robles Muñoz, Guillermo

Bachelor’s thesis in pdf

Abstract – Several manners of extracting energy have become popular in the last years. In particular, energy from magnetic fields captured by inductive principles is one of the most important methods regarding energy harvesting. Obtaining energy from high-power low-frequency signals is currently possible, but the aim of this report goes further. Partial discharge phenomena are revealed outside the insulation as high-frequency pulsing signals produced under high-voltage situations that contributes to the deterioration of the electrical machinery, causing even their failure. It is very important to localize this phenomenon in order to avoid possible futures breakdowns. This project demonstrates how to extract energy from high frequency inductive phenomena. Particularly, the feasibility to harvest energy from partial discharge occurrence is satisfactorily studied. Several energy levels are accumulated in a capacitor depending on the topology implemented. Energy from partial discharges pulses has not been accumulated to date. This report discuss a relation between the voltage across a capacitor and partial discharge events leading to a possible detection system.

 

Partial discharges and noise separation using spectral power ratios and genetic algorithms

31

J.M. Fresno, J.A. Ardila-Rey, J.M. Martínez-Tarifa, G. Robles, Partial discharges and noise separation using spectral power ratios and genetic algorithms. IEEE Transactions on Dielectrics and Electrical Insulation Vol. 24, Issue 1, pp. 31-38, January 2017

  • 2017 Impact Factor: 1.774
  • 73/146 (Q2) in ‘Physics, Applied’
  • Journal Impact Factor Percentile: 50.342
Abstract – Accurate measurements of partial discharge (PD) activity is essential for the application of this technique to condition-based monitoring. Noise and PD source characterization is necessary to fulfil that goal, since the interpretation of classical phase-resolved partial discharge (PRPD) patterns is usually complex for the measurements done in field. A successful pulse source separation prior to the identification seems to be the best option. The authors proposed in a previous work a method based on spectral power ratios (PR) to separate pulse sources with quite good experimental results. This technique calculates the spectral power in two frequency bands to obtain two parameters which, represented in a 2-dimensional map (PR map), characterize each pulse source by a cluster of points. The main difficulty of this technique is the choice of the appropriate frequency intervals that give a good separation of clusters, which sometimes can be cumbersome by manual means. Thus, this paper presents an unsupervised technique to select the two frequency intervals that gives the best separation among several clusters. This will give a great support for the system user to separate PD and noise sources in real measurements. The authors used genetic algorithms (GAs) to select these frequencies, with good results in several real experiments.
Keywords – Partial discharges, genetic algorithms, electrical insulation, power ratio maps, clustering techniques, spectral power, statistical dispersion.

Problemas resueltos de fundamentos de ingeniería eléctrica

 

Portada del libro Problemas resueltos de ingeniería eléctrica

http://www.paraninfo.es/catalogo/9788428337892/problemas-resueltos-de-ingenieria-electrica

En este libro se incluyen 100 problemas resueltos de ingeniería eléctrica. Su objetivo es servir de preparación para los exámenes de evaluación continua y exámenes finales de asignaturas relacionadas con la resolución de circuitos eléctricos. Son problemas que han sido tradicionalmente propuestos en exámenes de Teoría de circuitos  y de Fundamentos de ingeniería eléctrica.

Está dividido en cuatro partes fundamentales:

  • Corriente continua
  • Corriente alterna
  • Sistemas trifásicos
  • Transitorios de primer orden

La estructura de los ejercicios está pensada para que los estudiantes puedan medir su propio aprendizaje. En cada uno de ellos se puede conseguir el aprobado en un tiempo razonable y siempre se incluye una pregunta de mayor dificultad que permite distinguir quién ha desarrollado capacidades adicionales frente a los que simplemente han entendido los conceptos básicos. Asimismo, los ejercicios se ordenan por su grado dificultad y por los conceptos fundamentales que evalúan. Al comienzo de cada capítulo se encuentran cuestiones básicas que se deben poder resolver en un tiempo limitado de diez minutos y a continuación se encuentran problemas con varios apartados y con la puntuación que se asigna a cada uno de ellos.

El libro Problemas resueltos de fundamentos de ingeniería eléctrica está también disponible en:

Casa del libro

Amazon.es

IberLibro.com

 

 

Antennas in Partial Discharge Sensing System

Robles G., Albarracín R., Vázquez J.L. (2015) Antennas in Partial Discharge Sensing System. In: Chen Z. (eds) Handbook of Antenna Technologies. Springer, Singapore

Received: 26 September 2014; Accepted: 23 June 2015; First Online: 22 August 2015

Publisher Name: Springer, Singapore

Online ISBN: 978-981-4560-75-7

DOI: https://doi.org/10.1007/978-981-4560-75-7_95-1

Chapter: http://link.springer.com/referenceworkentry/10.1007/978-981-4560-75-7_95-1

Published in the Handbook of Antenna Technologies: http://link.springer.com/referencework/10.1007/978-981-4560-75-7

Abstract

The exponential growing demand of electricity has stimulated the manufacture of electric equipment with high rated powers withstanding tens and hundreds of kilovolts. These devices have to be insulated to ensure a safe and reliable service while their size and cost are reduced. Unfortunately, insulations deteriorate over time by being in operation under load and exposed to harsh environments that can degrade their behavior and lead to unexpected equipment outages and failures. The continuous monitoring of these assets is paramount in the operation of electric power systems, and one of the most popular methods to evaluate the ageing is the detection of partial discharges. Partial discharges are ionization processes that take place in voids filled with gas or oil inside the insulation, in dielectric surfaces, and in the proximity of sharp metallic objects. The chemical and physical structure of the insulation is changed, and eventually weakened, by the continuous action of the discharges. Then, their apparition can be directly a signal of problems in the insulation, but they can also be the consequence of other degradation processes. Partial discharges can be measured with a wide range of detectors including inductive, capacitive, acoustic, and light sensors. Because partial discharges occur in extremely short times, well below 1 ns, the radiofrequency measurement of the phenomenon in the HF, VHF, and UHF bands is also part of the unconventional methods used for their detection. EM sensors or antennas have the ability of performing a complete study on the measurement of partial discharges. They can detect pulses, localize the partial discharge site, and, to some extent, classify the type of partial discharge online. However, one of the most important challenges when using antennas in the diagnostic of insulations is the difficulty of relating the RF emissions to the severity of the PD. Another determent in the wide application of antennas as partial discharge detectors is the sample rate needed to obtain information from the signals in the time and frequency domains. The chapter also explores the most common configurations of antennas used in the detection of partial discharges as well as how they are installed and used in different electrical machines.

Keywords

Partial discharges Ultrahigh-frequency detection techniques Electrical insulation diagnosis Sensors Instrumentation Electrical measurements Ultrahigh-frequency measurements Antenna parametrization Electrical maintenance

Spatial study of the uncertainties in the localization of partial discharges for different antenna layouts

Fresno, J.; Robles, G.; Martinez-Tarifa, J.; Stewart, B.; Spatial study of the uncertainties in the localization of partial discharges for different antenna layouts. 2017 IEEE International Instrumentation and Measurement Techonology Conference, Torino (Italy), May 22-25, 2017

https://doi.org/10.1109/I2MTC.2017.7969802

Abstract—The maintenance of high-voltage equipment is paramount to avoid blackouts or the interruption of electrical service. One of the most reliable methods to know the status of insulation systems is the measurement of partial discharges (PD). This phenomenon occurs when the dielectric presents imperfections due to ageing and degradation processes. Partial discharges are sudden releases of charge that can emit energy in a wide band of frequencies even in UHF. Therefore, antennas can be used, not only to detect the occurrence of PD, but to locate the source of emission and, consequently, the damaged asset. The localization can be done using multilateration measuring the time-differences of arrival (TDOA) of the pulses to an array of antennas. However, the onset of the signal is difficult to define due to numerous issues, from low signal-to-noise ratio, to lack of line-of-sight or errors in the positioning of the antennas. Then, the position of the source may have large uncertainties that even can prevent finding the asset at stake. The configuration of the antenna layout can help to minimize the effect of the uncertainties in the measurement of the TDOA. It has been found that there are configurations that favour certain bearings when locating the source giving more accurate results. This paper explores three type of antenna layouts and devises a method to determine what directions are best to orient the array.

Keywords—Antennas, Radio-frequency, Localization, Partial Discharges.

A survey of time-of-flight algorithms to determine bone positions in movement

Fresno, J.; Giannetti, R; Robles, G. A survey of time-of-flight algorithms to determine bone positions in movement. 2017 IEEE International Instrumentation and Measurement Techonology Conference, Torino (Italy), May 22-25, 2017

https://doi.org/10.1109/I2MTC.2017.7969710

Abstract—In biomechanical applications where an ultrasound signal is used to determine the position of a specific organ or tissue, like for example a bone, a so-called A-mode ultrasonography is used. A ultrasonic pulse is generated by a transducer, injected in the tissue to be examined, and then the echoes are received and processed. Echoes are generated by changes in acoustic impedance in the medium, like for example a change of tissue from muscle to bone. To determine the position of the reflecting interface, the time-of-flight is measured and, utilizing well-know values for the transmission speed, the distance or depth is computed. If the localization device is to be designed to be small, wearable, and low-power, it is expected that the signal will be of worse quality with respect to traditional ultrasonography systems, especially under the point of view of signal-to-noise ratio. In these conditions, the reliability of the algorithm that implement the time-of-flight calculation is of paramount importance. In this paper, a simulated soft tissue–bone interface (implemented with an ultrasound gel-pad) has been measured with intentionally low excitation signals and with the presence of imperfections similar to those expected in a physiological system. Several classic algorithms have been tested and benchmarked in this condition, and a new method with better reliability and repeatability is proposed.

Keywords—Time-of-flight, ultrasonic sensors, biomecanical systems, cross-correlation, kurtosis.

The influence of antenna positioning errors on the radio-frequency localization of partial discharges sources

Open access: http://www.mdpi.com/2504-3900/1/2/12/

Fresno, J.; Robles, G.; Stewart, B.; Martinez-Tarifa, J. The influence of antenna positioning errors on the radio-frequency localization of partial discharges sources. In Proceedings of the 3rd Int. Electron. Conf. Sens. Appl., 15–30 November 2016; Sciforum Electronic Conference Series, Vol. 3, 2016 , E003; doi:10.3390/ecsa-3-E003

Abstract—Electrical insulation can have imperfections due to manufacturing or ageing. When the insulation is electrically stressed, discharges may happen in these inhomogeneous imperfect locations resulting in partial discharge (PD) which have very fast rise times and short time durations. Since charges are accelerated within PD activity, radiated electromagnetic energy across a wide bandwidth of frequencies can occur. The measurement of the radiated PD energy is widely employed to identify defective insulation within high voltage equipment. Based on assessment of the strength and nature of the emitted PD signals, determination is made to carry out predictive maintenance in order to prevent equipment breakdown. The location of emitted radiated PD signals may be determined using multi-lateration techniques using an array of at least 4 antennas. Depending on the relative position between the antennas and the PD source, the radiated emissions from the PD source arrive at each antenna at different times. The relative time differences of arrivals (TDOA) together with the antennas position are variables used to locate the PD source in 3D space. The effect on the location error of a PD source using TDOA calculations based on acquisition sample time errors is a topic which has previously been studied (see bibliography). This paper now investigates the accuracy on PD location as a consequence of error on the measured positions of the antennas. This paper evaluates the influence of positional antenna error on the possible accuracy of the localization of the PD source. This error is analyzed for 3 different antenna array layouts and for different vector directions from the arrays. Additionally, the least sensitive layout with regard to positioning errors is proposed to assist in improving the location accuracy of PD sources.

Keywords—Radio-Frequency Localization; Partial Discharges; Antennas Positioning; Measurement Error.