Development of high-capacity substation connectors compatible with HTLS technology
- Autores: Francesca Capelli
- Directores de la Tesis: Jordi-Roger Riba Ruiz (dir. tes.)
- Lectura: En la Universitat Politècnica de Catalunya (UPC) ( España ) en 2017
- Idioma: inglés
- Tribunal Calificador de la Tesis: Joan Esteve Pujol (presid.), E. Rupérez (secret.), Andrea Cavallini (voc.)
- Programa de doctorado: Programa de Doctorado en Ingeniería Eléctrica por la Universidad Politécnica de Catalunya
- Materias:
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- Resumen
The advent of HTLS (High Temperature, Low Sag) conductors imposes more severe operating conditions on devices such as substation connectors intended for transmission and distribution systems, which are subjected to higher loads and have to operate at higher temperatures. The main objective of this thesis is the development of a new family of high-capacity substation connectors compatible with the HTLS technology. The first aspect that has been analyzed is the selection of the base material. At present, substation connectors are manufactured by using A356 cast aluminum alloy due to its good castability and physical properties. However, due to the new operating conditions introduced by the HTLS technology, A356 alloy needs to be further improved. A chemical treatment (modification) has been proposed to fulfill the requirements of high-capacity substation connectors¿ material. Experimental measurements of electrical, thermal and mechanical properties have been carried out to characterize and compare properties of both un-modified and modified alloys. Moreover, their electrical resistivity has been evaluated from cryogenic up to 200 ºC, to find out the temperature coefficient of resistivity. Experimental measurements prove that chemical modification improves mechanical, electrical and thermal properties of A356.0 alloy. Moreover, to design the new family of connectors it is necessary to take into account the contact resistance. The contact resistance defines the energy-efficiency, the stable performance and the long-term service of an electrical connection. To reduce the contact resistance a new installation procedure has been proposed in this thesis. Thermal behavior of connectors installed with the new procedure has been compared with the traditional one, through standardized temperature rise, thermal cycle and short-circuit tests. Results show a lower operating temperature and degradation rate for connectors installed with the new procedure. Moreover, the temperature coefficient of contact resistance has been determined through an experimental test. To accurately predict the thermal behavior of substation connectors, it is important to estimate the electrical constriction resistance (ECR). Different ECR models have been compared with experimental measurements. The fractal model for rough surfaces shows closer agreement with experimental data, however, they are based on several parameters dependent on the surfaces¿ roughness, whose values need to be tuned for each application. A software tool based on a genetic algorithm approach has been developed to obtain an accurate prediction of the contact resistance. Furthermore, advanced 3D-FEM modelling tools to perform realistic simulations of the short-time and peak withstand current and temperature rise tests have been developed. Substation connectors must pass these compulsory tests, which require high-power laboratory facilities, are very power-consuming and thus very expensive. The development of a realistic simulation tool is essential for anticipating the results of the mandatory laboratory tests in a fast and inexpensive way. In this thesis electromagnetic-thermal multiphysics 3D-FEM tools to simulate the transient thermal behavior of substation connectors during the standard short-circuit and temperature rise tests have been developed. Finally the thesis deals with the loop inductance. The estimation of the loop inductance is very important as it determines voltage drop in conductors. Inductance estimation provided by formulas has been compared with FEM simulations and experimental measurements. Furthermore, a simple setup to reduce the reactive power consumption when conducting short-circuit tests, based on placing a conductor forming a closed inner loop concentric with the testing loop, has been proposed and optimized trough 3D-FEM simulations.
