Francesca Capelli
Polytechnic University of Catalonia
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Featured researches published by Francesca Capelli.
IEEE Transactions on Instrumentation and Measurement | 2017
Francesca Capelli; Jordi-Roger Riba; Elisa Rupérez; Josep Sanllehi
The electrical contact resistance greatly influences the thermal behavior of substation connectors and other electrical equipment. During the design stage of such electrical devices, it is essential to accurately predict the contact resistance to achieve an optimal thermal behavior, thus ensuring contact stability and extended service life. This paper develops a genetic algorithm (GA) approach to determine the optimal values of the parameters of a fractal model of rough surfaces to accurately predict the measured value of the surface roughness. This GA-optimized fractal model provides an accurate prediction of the contact resistance when the electrical and mechanical properties of the contacting materials, surface roughness, contact pressure, and apparent area of contact are known. Experimental results corroborate the usefulness and accuracy of the proposed approach. Although the proposed model has been validated for substation connectors, it can also be applied in the design stage of many other electrical equipments.
international conference on industrial technology | 2015
Francesca Capelli; Jordi-Roger Riba; David González
One of the main problems that arises when performing short-circuit tests to large loops involving substation connectors is the inductive component of the loop impedance. Transformers used to perform short-circuit tests have a secondary winding with very few turns, producing a very low output voltage. The increase in the reactive component of the impedance, which is related to loop size, limits the current output capacity, because the reactive component tends to saturate the output of the transformer and absorbs large amounts of reactive power. This paper analyzes a simple method to minimize the power requirements when conducting short-circuit tests, based on the reduction of reactive power consumption during the test. It is based on placing a wired conductor forming a closed inner loop concentric with the testing loop. The decrease of reactive power is related to the effect of the mutual inductance between the inner and outer loops. Three-dimensional finite element method (3D-FEM) simulations are used to optimize the problem, allowing changing the geometric and material properties of the inner loop. Experimental results validate the simulation method applied in this work to optimize the short-circuit tests.
2016 10th International Conference on Compatibility, Power Electronics and Power Engineering (CPE-POWERENG) | 2016
Francesca Capelli; Jordi-Roger Riba; David González
The contact resistance is the key variable that characterizes the stable performance and long-term service of an electrical connection. It is worth noting that the contact resistance in substation connectors can be several times that of the connectors resistance. To reduce connection losses and thus decrease connectors operating temperature, it is important to minimize contact resistance. The aim of this work is to characterize the relationship between the surface preparation, the resulting contact resistance and the thermal performance of substation connectors. First, the thermal behavior of substation connectors assembled with the traditional and a new installation method proposed by the authors has been characterized. It has been done by means of experimental temperature rise test and current cycle test. Thanks to these results, it has been proved that the new installation procedure allows reducing connectors temperature in operating conditions as well as the variability of the electrical resistance among different samples due to thermal stress. Moreover, by means of experimental measurements, the temperature dependence of the contact resistance has been analyzed, with the objective to characterize the performance of an electrical contact under different operating temperatures. To determine the temperature coefficient of the contact resistance, an experimental resistance measurement has been continuously performed during the cooling of a contact interface, previously heated at 200 °C. This value can be very useful for an optimal design of the substation connectors.
International Journal of Electrical Engineering Education | 2018
Jordi-Roger Riba; Francesca Capelli
This article analyzes the inductance of different conductive nonmagnetic conductors’ configurations under alternating current supply. The inductance is a key design parameter in tracks of electronic devices, power transmission and distribution systems, and lightning, grounding, and bonding systems. Inductance highly relies on the problem geometry, and under AC supply, it is also influenced by skin and proximity effects. The inductance significantly determines voltage drop in conductors, thus increasing reactive power consumption and limiting conductors’ ampacity. Although this is an important topic, it is seldom studied in detail in undergraduate and even in graduate physics and engineering studies. To this end, this paper compares the results provided by existing closed formulas for simple conductors’ configurations with those attained through two-dimensional finite element method simulations. Finite element method based simulations are increasingly being incorporated in the syllabuses of graduate and undergraduate courses due to their accurate solutions and flexibility, since finite element method models can be applied in a wide range of electrical frequencies and configurations, some of which do not have an analytical solution. The finite element method based approach presented in this paper has been found a valuable complement to the lectures and assignments in electricity courses for engineering students.
ieee international conference on power system technology | 2016
Carlos Abomailek; Francesca Capelli; Jordi-Roger Riba; Pau Casals-Torrens; Manuel Moreno-Eguilaz
This paper proposes a fast and accurate method to simulate the temperature rise due to a short-circuit condition in power conductors of aluminum based on one-dimensional reduction and the application of the finite difference method (FDM). The method suggested discretizes the analyzed conductor into several small one-dimensional nodes or elements. To improve accuracy and speed, the transient method proposed here applies a one-dimensional approach but analyzing in each node, the three-dimensional geometry of the conductor. By this way, and at each time-step, the convective coefficient and the incremental resistance of each node are determined and a further energy balance is calculated, thus obtaining realistic and accurate results. Results attained by means of the proposed method are validated against finite element method (FEM) simulations and experimental results conducted in a power laboratory, which corroborate the usefulness and accurate results of the proposed method.
ieee international conference on power system technology | 2016
Francesca Capelli; Carlos Abomailek; Jordi-Roger Riba; Josep Sanllehi
The contact resistance is a key parameter that has a great impact on the thermal behavior, stable performance and efficiency of electrical devices containing electrical contacts thus greatly influencing the useful life of such devices. The study and minimization of the contact resistance is especially critical when dealing with contact surfaces made of aluminum, due to the insulating nanometric alumina layer formed when the aluminum is in contact with atmospheric air. This is the case of substation connectors, most of which are made of aluminum alloy. When applying procedures to eliminate this insulating layer, the only component of the contact resistance is the electrical constriction resistance or ECR. This paper analyzes the accuracy of different available ECR models. The study is carried out by comparing the results of the theoretical models with experimental data, obtained when analyzing different substation connectors and aluminum conductors. The results of this work can be very useful during the optimal design stage of such devices, to ensure a suitable thermal behavior.
Advances in Electrical and Computer Engineering | 2016
Francisco Giacometto; Francesca Capelli; José Luis Romeral Martínez; Jordi-Roger Riba Ruiz; Enric Sala
Temperature rise simulations are one of the key steps in the design of high-voltage substation connectors. These simulations help minimizing the number of experimental tests, which are ...
conference of the industrial electronics society | 2015
Francisco Giacometto; Francesca Capelli; Enric Sala; Jordi Riba; Luis Romeral
A wide study regarding the suitability of data-driven modelling applied to the prediction of thermal convection responses on substation connectors is presented in this paper. The study starts with the compilation of a database with thermal profiles obtained from a finite element method simulation (FEM). Afterwards, we applied partitioning methods in order to increase the number of data sets used for modelling and later evaluate the stability of the learning algorithms. After the modeling process, the accuracy of the model per each data set is measured and the statistics about the errors are analyzed. Normality test are applied to measure the error variance. They bring us information about the error distribution and the stability of the learning algorithms. The study finish when it probes that any data-driven model is computationally less time expensive than any FEM simulation running on this study. Experimental work also confirms that the accuracy of the data-driven models: cascade feed forward neural network and feed forward neural network, can replace the FEM simulations; providing a high accuracy and a low error variance while speeding up the simulation time.
Energies | 2016
Francesca Capelli; Jordi-Roger Riba; Joan Pérez
Iet Generation Transmission & Distribution | 2018
Jordi-Roger Riba; Carlos Abomailek; Pau Casals-Torrens; Francesca Capelli