Development of reduced-scale tests for HTLS substation connectors

Power distribution networks face the upcoming challenge of managing the increase of power demand predicted worldwide. Power grid capacity is limited by the number of lines deployed and their characteristics, including conductor section, spacing, or number of phases, among others. Building new lines is costly and faces population opposition in many places. Therefore, a new conductor technology designed to upgrade the existing power lines has arisen. This technology, known as High Temperature Low-Sag (HTLS), permits the rise of capacity of existing power lines without modifying the supporting structures. Nowadays, the conductor technology is mature and under commercialization. But, there is the need to design and assess the behaviour of some auxiliary accessories needed to operate power lines equipped with HTLS conductors. Specifically, the substation connector industry is still developing HTLS substation connectors. From all the design process, the validation of the performance of these products is still a milestone. Currently, the tests performed to hardware for power lines are costly in terms of required infrastructures, testing time, power requirements, monetary cost and environmental affectation. Moreover, many of these tests can only be performed in few facilities all around the world. Furthermore, from an industrial scope, there is a growing interest to obtain the data of such tests in onsite industrial laboratories. Thus, this thesis develops a set of reduced-scale tests equivalent to the ones performed on full-scale connectors to validate the performance of the new designs. This thesis also performs a critical review of some of the methodologies that currently are being applied to assess products lifetime, and proposes the use of modern approaches. Concluding, this document aims to develop a series of test procedures that provide data about the validity of the newly required substation connectors designs in a cheaper, faster, and environmentally-friendlier way, whilst allowing to test the connectors in industrial laboratories, which have much less requirements than those of the full-scale test, since the later often require to be carried out in singular and scarce facilities.Las redes de distribución y transmisión de potencia se enfrentan al reto de manejar el incremento de demanda eléctrica previsto mundialmente. La capacidad de la red eléctrica está limitada por el número de líneas instaladas y sus características. Esto incluye, la sección del conductor, espaciado o número de fases, entre otros. La construcción de nuevas líneas es cara y en muchos casos imposible debido a la enorme oposición a la que se enfrentan en muchos lugares del mundo. Por ello, en los últimos años una nueva tecnología de conductores ha empezado a tomar importancia. Estos conectores conocidos como HTLS (alta temperatura baja flecha), permiten el aumento de la capacidad de las líneas eléctricas existentes sin por ello tener que modificar las estructuras que las soportan. Hoy en día, esta tecnología está suficientemente madura para ser comercializada. Sin embargo, existe la necesidad de diseñar y validar el comportamiento de una serie de accesorios auxiliares para líneas eléctricas. Concretamente, la industria de los conectores de subestación está desarrollando sus productos para líneas HTLS. El proceso de validación de estos conectores es aún un hito por alcanzar. Por el momento, los ensayos realizados sobre aparamenta para líneas eléctricas son costosos en términos de infraestructuras necesarias, tiempo de ensayo, potencia requerida, coste económico e impacto medioambiental. Además, muchos de estos ensayos sólo pueden llevarse a cabo en unas pocas instalaciones disponibles en todo el mundo. Por lo tanto, desde un punto de vista industrial, existe un creciente interés en obtener estos datos en laboratorios industriales. Por ello, esta tesis desarrolla un conjunto de ensayos a escala reducida equivalentes con los que hoy en día se realizan a escala real, con el fin de validar el rendimiento de los nuevos diseños de conector. Esta tesis también realiza una revisión crítica de algunas de las metodologías que hoy en día se llevan a cabo para estudiar el envejecimiento de los conectores de subestación. A su vez, propone el uso de metodologías más modernas para realizar dichos estudios. En conclusión, este documento desarrolla una serie de procedimientos de ensayo para validar los diseños de los nuevos desarrollos de conectores de subestación de una manera barata, rápida y respetuosa con el medio ambiente a la vez que permite el ensayo de dichos productos en laboratorios industriales

Development of reduced-scale tests for HTLS substation connectors

Power distribution networks face the upcoming challenge of managing the increase of power demand predicted worldwide. Power grid capacity is limited by the number of lines deployed and their characteristics, including conductor section, spacing, or number of phases, among others. Building new lines is costly and faces population opposition in many places. Therefore, a new conductor technology designed to upgrade the existing power lines has arisen. This technology, known as High Temperature Low-Sag (HTLS), permits the rise of capacity of existing power lines without modifying the supporting structures. Nowadays, the conductor technology is mature and under commercialization. But, there is the need to design and assess the behaviour of some auxiliary accessories needed to operate power lines equipped with HTLS conductors. Specifically, the substation connector industry is still developing HTLS substation connectors. From all the design process, the validation of the performance of these products is still a milestone. Currently, the tests performed to hardware for power lines are costly in terms of required infrastructures, testing time, power requirements, monetary cost and environmental affectation. Moreover, many of these tests can only be performed in few facilities all around the world. Furthermore, from an industrial scope, there is a growing interest to obtain the data of such tests in onsite industrial laboratories. Thus, this thesis develops a set of reduced-scale tests equivalent to the ones performed on full-scale connectors to validate the performance of the new designs. This thesis also performs a critical review of some of the methodologies that currently are being applied to assess products lifetime, and proposes the use of modern approaches. Concluding, this document aims to develop a series of test procedures that provide data about the validity of the newly required substation connectors designs in a cheaper, faster, and environmentally-friendlier way, whilst allowing to test the connectors in industrial laboratories, which have much less requirements than those of the full-scale test, since the later often require to be carried out in singular and scarce facilities.Las redes de distribución y transmisión de potencia se enfrentan al reto de manejar el incremento de demanda eléctrica previsto mundialmente. La capacidad de la red eléctrica está limitada por el número de líneas instaladas y sus características. Esto incluye, la sección del conductor, espaciado o número de fases, entre otros. La construcción de nuevas líneas es cara y en muchos casos imposible debido a la enorme oposición a la que se enfrentan en muchos lugares del mundo. Por ello, en los últimos años una nueva tecnología de conductores ha empezado a tomar importancia. Estos conectores conocidos como HTLS (alta temperatura baja flecha), permiten el aumento de la capacidad de las líneas eléctricas existentes sin por ello tener que modificar las estructuras que las soportan. Hoy en día, esta tecnología está suficientemente madura para ser comercializada. Sin embargo, existe la necesidad de diseñar y validar el comportamiento de una serie de accesorios auxiliares para líneas eléctricas. Concretamente, la industria de los conectores de subestación está desarrollando sus productos para líneas HTLS. El proceso de validación de estos conectores es aún un hito por alcanzar. Por el momento, los ensayos realizados sobre aparamenta para líneas eléctricas son costosos en términos de infraestructuras necesarias, tiempo de ensayo, potencia requerida, coste económico e impacto medioambiental. Además, muchos de estos ensayos sólo pueden llevarse a cabo en unas pocas instalaciones disponibles en todo el mundo. Por lo tanto, desde un punto de vista industrial, existe un creciente interés en obtener estos datos en laboratorios industriales. Por ello, esta tesis desarrolla un conjunto de ensayos a escala reducida equivalentes con los que hoy en día se realizan a escala real, con el fin de validar el rendimiento de los nuevos diseños de conector. Esta tesis también realiza una revisión crítica de algunas de las metodologías que hoy en día se llevan a cabo para estudiar el envejecimiento de los conectores de subestación. A su vez, propone el uso de metodologías más modernas para realizar dichos estudios. En conclusión, este documento desarrolla una serie de procedimientos de ensayo para validar los diseños de los nuevos desarrollos de conectores de subestación de una manera barata, rápida y respetuosa con el medio ambiente a la vez que permite el ensayo de dichos productos en laboratorios industriales.Postprint (published version

Reduced scale feasibility of temperature rise tests in substation connectors

Due to the important increase of the power of electrical transmission and distribution grids expected for the following years, especially in developing countries such as Kenya, Brazil, Philippines or Mexico among others, that have planes of generating energy from clean sources far away from the centres of consumption [1] it becomes a matter of special importance adapting and developing new substation connectors’ testing methods according to the power and temperature regimes at which they are expected to work. The international normative frame of substation connectors established both by the International Electrotechnical Committee (IEC) [2] and the National Electrical Manufacturers Association (NEMA) [3] sets standardized tests for the evaluation of high voltage connectors. These tests are routinely done within the quality plans of the manufacturers. At the moment, testing of substation connectors –and in general switchgear and fittings- is time demanding and costly due to the energy consumed by such tests. The expectations for the following years are that the power consumption of these tests will not do nothing but grow due to expected increase of power of worldwide overhead lines. For instance, today temperature rise tests in substation connectors involve power ranges up to 100 kVA, which are applied in cycles that can last several weeks. These tests are only feasible in few laboratories and at a very high cost: temporary, monetary, energetic and environmental. For this reason, following the line of other technologies such as aeronautics, naval engineering, or automotive as well as other studies done in the field of electrical engineering specially related to the corona effect [4], this study proposes to develop a reduced scale test system to perform temperature rise tests for substation connectors. Both, a theoretical framework based on analytical formulas, finite element method (FEM) simulations and experimental data has been developed to conduct reduced scale temperature rise tests and to set the conditions at which they provide comparable results to those attained in the original scale tests. Firstly, two circular loops (original and reduced scale loops) composed of a power conductor and two terminal connectors were analysed. The aim of this first study was to determine in an easy and trustful way the voltage and current values to be applied in experimental reduced scale tests to achieve the same steady-state temperature as in the original scale temperature rise test. The scale relationship between tests was set in 1:1.8, although the method proposed in this study can deal with any other scale factor. This study was useful in order to have a first sight of the final results of the procedure using substation connectors.Postprint (published version

Transient thermal modelling of substation connectors by means of dimensionality reduction

This paper proposes a simple, fast and accurate simulation approach based on one-dimensional reduction and the application of the finite difference method (FDM) to determine the temperatures rise in substation connectors. The method discretizes the studied three-dimensional geometry in a finite number of one-dimensional elements or regions in which the energy rate balance is calculated. Although a one-dimensional reduction is applied, to ensure the accuracy of the proposed transient method, it takes into account the three-dimensional geometry of the analyzed system to determine for all analyzed elements and at each time step different parameters such as the incremental resistance of each element or the convective coefficient. The proposed approach allows fulfilling both accuracy and low computational burden criteria, providing similar accuracy than the three-dimensional finite element method but with much lower computational requirements. Experimental results conducted in a high-current laboratory validate the accuracy and effectiveness of the proposed method and its usefulness to design substation connectors and other power devices and components with an optimal thermal behavior.Postprint (published version

Simplification and cost reduction of visual corona tests

Peer ReviewedPostprint (author's final draft

Application of reduced scale tests to improve the thermal performance of high-voltage substation connectors

Peer ReviewedPostprint (author's final draft

Feasibility analysis of reduced-scale visual corona tests in high-voltage laboratories

Corona is a critical effect that must be considered during the design and optimization stages of high-voltage hardware such as substation connectors, since due to the harmful effects, corona threats power systems reliability. Visual corona tests allow detecting and identifying the critical corona points on the surface of substation connectors, so corrective actions can be applied for product optimization. This paper focuses on reduced-scale visual corona tests intended to verify and optimize the behaviour of such high-voltage hardware. Reduced-scale visual corona tests allow reducing the voltage to be applied, laboratory size, instrumentation requirements, assembly and test times, and finally the overall costs of the tests compared to standard corona tests carried out in large-size high-voltage laboratories. A hybrid approach combining experimental tests and finite element method (FEM) simulations is presented, which allows obtaining the equivalent visual corona onset voltage between reduced-scale and full-scale tests. Although the paper focuses on the analysis of aluminium substation connectors, the proposed approach can be applied to many other hardware intended for high-voltage applications.Peer ReviewedPostprint (author's final draft

Fast electro-thermal simulation of short-circuit tests

Peer ReviewedPostprint (author's final draft

Development of reduced-scale tests for HTLS substation connectors

Power distribution networks face the upcoming challenge of managing the increase of power demand predicted worldwide. Power grid capacity is limited by the number of lines deployed and their characteristics, including conductor section, spacing, or number of phases, among others. Building new lines is costly and faces population opposition in many places. Therefore, a new conductor technology designed to upgrade the existing power lines has arisen. This technology, known as High Temperature Low-Sag (HTLS), permits the rise of capacity of existing power lines without modifying the supporting structures. Nowadays, the conductor technology is mature and under commercialization. But, there is the need to design and assess the behaviour of some auxiliary accessories needed to operate power lines equipped with HTLS conductors. Specifically, the substation connector industry is still developing HTLS substation connectors. From all the design process, the validation of the performance of these products is still a milestone. Currently, the tests performed to hardware for power lines are costly in terms of required infrastructures, testing time, power requirements, monetary cost and environmental affectation. Moreover, many of these tests can only be performed in few facilities all around the world. Furthermore, from an industrial scope, there is a growing interest to obtain the data of such tests in onsite industrial laboratories. Thus, this thesis develops a set of reduced-scale tests equivalent to the ones performed on full-scale connectors to validate the performance of the new designs. This thesis also performs a critical review of some of the methodologies that currently are being applied to assess products lifetime, and proposes the use of modern approaches. Concluding, this document aims to develop a series of test procedures that provide data about the validity of the newly required substation connectors designs in a cheaper, faster, and environmentally-friendlier way, whilst allowing to test the connectors in industrial laboratories, which have much less requirements than those of the full-scale test, since the later often require to be carried out in singular and scarce facilities.Las redes de distribución y transmisión de potencia se enfrentan al reto de manejar el incremento de demanda eléctrica previsto mundialmente. La capacidad de la red eléctrica está limitada por el número de líneas instaladas y sus características. Esto incluye, la sección del conductor, espaciado o número de fases, entre otros. La construcción de nuevas líneas es cara y en muchos casos imposible debido a la enorme oposición a la que se enfrentan en muchos lugares del mundo. Por ello, en los últimos años una nueva tecnología de conductores ha empezado a tomar importancia. Estos conectores conocidos como HTLS (alta temperatura baja flecha), permiten el aumento de la capacidad de las líneas eléctricas existentes sin por ello tener que modificar las estructuras que las soportan. Hoy en día, esta tecnología está suficientemente madura para ser comercializada. Sin embargo, existe la necesidad de diseñar y validar el comportamiento de una serie de accesorios auxiliares para líneas eléctricas. Concretamente, la industria de los conectores de subestación está desarrollando sus productos para líneas HTLS. El proceso de validación de estos conectores es aún un hito por alcanzar. Por el momento, los ensayos realizados sobre aparamenta para líneas eléctricas son costosos en términos de infraestructuras necesarias, tiempo de ensayo, potencia requerida, coste económico e impacto medioambiental. Además, muchos de estos ensayos sólo pueden llevarse a cabo en unas pocas instalaciones disponibles en todo el mundo. Por lo tanto, desde un punto de vista industrial, existe un creciente interés en obtener estos datos en laboratorios industriales. Por ello, esta tesis desarrolla un conjunto de ensayos a escala reducida equivalentes con los que hoy en día se realizan a escala real, con el fin de validar el rendimiento de los nuevos diseños de conector. Esta tesis también realiza una revisión crítica de algunas de las metodologías que hoy en día se llevan a cabo para estudiar el envejecimiento de los conectores de subestación. A su vez, propone el uso de metodologías más modernas para realizar dichos estudios. En conclusión, este documento desarrolla una serie de procedimientos de ensayo para validar los diseños de los nuevos desarrollos de conectores de subestación de una manera barata, rápida y respetuosa con el medio ambiente a la vez que permite el ensayo de dichos productos en laboratorios industriales

A 3D-FEM-based model to predict the electrical constriction resistance of compressed contacts

This work proposes a method to estimate the electrical constriction resistance of two mating metallic rough surfaces based on the finite element method (FEM). The FEM-based method generates a random array of three-dimensional orthogonal parallelepipeds to simulate the stochastic distribution of the asperities across the contact interface. The effect of the contact pressure is studied in detail, since once the contact materials and the topology of the contact area are settled, the contact pressure plays a critical role in determining the electrical constriction resistance. The proposed model is based on two critical variables, the contact pressure and the surface roughness of the mating surfaces, which must be measured in the laboratory to calibrate the model. Results provided by the FEM-based model are compared with experiments for three geometries, thus validating the accuracy of the proposed approach. Although the apparent contact areas of the analyzed specimens have a rectangular shape, the proposed method is also applicable to determine the electrical constriction resistance of other geometries. It is also proved that depending on the pressure applied to the contact interface, the electrical constriction resistance can be almost independent of the apparent area of contact. Although the aim of this work was to generate an electrical constriction resistance model for power connectors, it is also applicable to many other power devices.Peer ReviewedPostprint (author's final draft