Detection and reduction of high current turrets of GSU transformers - Part II

This article is the continuation of the paper: “Detection and reduction of high temperature in high current turrets of generator step-up (GSU) transformers – Part I” published in the April 2022 issue of “Transformers Magazine”, where the author demonstrated that the heating issue in the low voltage (LV) turrets of a 90 MVA GSU transformer is produced by the low carbon steel employed in the LV turret structure and by the presence of short non-magnetic stainless steel (SS) inserts located in the turrets which were manufactured by the original transformer manufacturer. This new article presents the magnetic solution for the heating issue found in the LV low carbon steel turrets of this 90 MVA GSU transformer. Utilizing Multiphysics finite element simulations and parametric analyses, the author demonstrates that modifying and varying the geometry of the original short SS inserts is possible to reduce the temperature in the low carbon steel turrets of the GSU transformer. This article demonstrates that by elongating and increasing the width of the original short SS inserts it is possible to reduce the temperature in the low carbon steel turrets of the GSU transformer. The magnetic solution presented in this article could be implemented on-site without the need to send the transformer to repair and avoid taking out of service the transformer for a long time

Temperature reduction in turrets - part I

This article presents the identification process of high temperatures in low voltage (LV) turrets of a single-phase generator step-up (GSU) transformer which is equipped with non-magnetic stainless steel (SS) inserts in the turrets. High temperatures are detected in the SS insert regions of the LV turrets utilizing thermography cameras and temperature labels. The presence of high temperature in the LV turrets generated issues in the transformer as the crystallization of the turret gasket seals and the presence of transformer oil leaks. To figure out the cause of the high temperature in the turrets, three-dimensional (3-D) finite element (FE) simulations are performed. Electromagnetic analyses coupled with thermal analyses are carried out to understand the origin of the high temperatures in the turrets of the GSU transformer. To validate the 3-D FE transformer model, the results of the FE simulations are compared with the temperature measurements in the turrets. With the FE simulation results, the author detected magnetic design issues related to the SS inserts and related to the magnetic material utilized in the turrets, which are producing high temperatures. The study presented could help transformer manufacturers to predict and prevent possible heating issues in GSU transformers in the LV turret regions

Thermal failure in a clamping bolt of a shunt reactor

This article presents the detection and analysis of a thermal failure produced in a core clamping bolt of a 5 MVAr gapped three-phase shunt reactor. Gases were detected in this shunt reactor during its operation at a substation in Mexico. Using dissolved gas analysis (DGA) and Duval’s triangle method, temperatures up to 700°C were estimated in the shunt reactor. Overheating evidence was detected in one of the core clamping bolts during an internal inspection of the shunt reactor. The author and the reactor manufacturer believe that the insulation of the clamping bolt was damaged by the loosening of the bolts produced by the vibration of the shunt reactor in conjunction with a possible low torque applied to the bolts. A short circuit between the bolt and the clamping frame was produced, generating the circulation of eddy currents in the bolt producing high temperatures and gasifying the insulating oil in the shunt reactor. Three-dimensional (3-D) finite element (FE) simulations were performed to verify the cause of the overheating issue in the clamping bolt of the shunt reactor, simulating the short circuit between the clamping bolt and the core frame. From the simulation results, the author determined that a short circuit between the bolt and the core frame generated the gases and the high temperatures in the shunt reactor. Finally, the manufacturer of the shunt reactor decided to reinforce the insulation of the clamping bolts using fiberglass to avoid future possible short circuit failures

Thermal failure in a clamping bolt of a shunt reactor

This article presents the detection and analysis of a thermal failure produced in a core clamping bolt of a 5 MVAr gapped three-phase shunt reactor. Gases were detected in this shunt reactor during its operation at a substation in Mexico. Using dissolved gas analysis (DGA) and Duval’s triangle method, temperatures up to 700°C were estimated in the shunt reactor. Overheating evidence was detected in one of the core clamping bolts during an internal inspection of the shunt reactor. The author and the reactor manufacturer believe that the insulation of the clamping bolt was damaged by the loosening of the bolts produced by the vibration of the shunt reactor in conjunction with a possible low torque applied to the bolts. A short circuit between the bolt and the clamping frame was produced, generating the circulation of eddy currents in the bolt producing high temperatures and gasifying the insulating oil in the shunt reactor. Three-dimensional (3-D) finite element (FE) simulations were performed to verify the cause of the overheating issue in the clamping bolt of the shunt reactor, simulating the short circuit between the clamping bolt and the core frame. From the simulation results, the author determined that a short circuit between the bolt and the core frame generated the gases and the high temperatures in the shunt reactor. Finally, the manufacturer of the shunt reactor decided to reinforce the insulation of the clamping bolts using fiberglass to avoid future possible short circuit failures

Capital humano, relacional y estructural en la actividad innovadora de las pequeñas y medianas empresas

Este estudio empírico busca medir la influencia que ejercen el capital humano, relacional y estructural en la actividad innovadora de estas empresas del Estado de Aguascalientes, México. El capital humano, relacional y estructural, como componentes del capital intelectual, han sido considerados como factores elementales para el desempeño innovador de las PYMES. Aunado a esto, al establecer a la innovación como una acción constante en su desempeño, las sitúa en destacados niveles de competitividad. De esta forma, el presente artículo procura demostrar la influencia del capital humano, relacional y estructural en la actividad innovadora de las PYMES de Aguascalientes

A bibliographic analysis of transformer literature 1990-2000

This paper presents an analysis of the bibliography on transformers covering the period from 1990 to 2000. It contains all the transformer subjects: a) Transformer design, b) Transformer protection, c) Transformer connections, d) Transformer diagnostics, e) Transformer failures, f) Transient analysis of transformers (overvoltages, overcurrents), g) Modeling and analysis of transformer using FEM (thermal modeling, losses modeling, insulation modeling, windings modeling). Several international journals were investigated including the following: Advances in Electrical and Computer Engineering, Canadian Journal of Electrical and Computer Engineering, COMPEL (The International Journal for Computation and Mathematics in Electrical and Electronic Engineering), Electrical Engineering, Electric Power Components and Systems, Electric Power Systems Research, European Transactions on Electrical Power, IEEE Transactions on Magnetics, IEEE Transactions on Power Delivery, International Journal of Electrical Power and Energy Systems, and IET Generation Transmission & Distribution. Due to the high number of publication in journals, we are not considering publications of conferences and symposia. A total of 700 publications are analyzed in this paper. The research presented in this paper is important because it contains and analyzes the best research papers on transformers coming from many countries all over the world and published in top rated scientific electrical engineering journals

Detection and reduction of high current turrets of GSU transformers - Part II

This article is the continuation of the paper: “Detection and reduction of high temperature in high current turrets of generator step-up (GSU) transformers – Part I” published in the April 2022 issue of “Transformers Magazine”, where the author demonstrated that the heating issue in the low voltage (LV) turrets of a 90 MVA GSU transformer is produced by the low carbon steel employed in the LV turret structure and by the presence of short non-magnetic stainless steel (SS) inserts located in the turrets which were manufactured by the original transformer manufacturer. This new article presents the magnetic solution for the heating issue found in the LV low carbon steel turrets of this 90 MVA GSU transformer. Utilizing Multiphysics finite element simulations and parametric analyses, the author demonstrates that modifying and varying the geometry of the original short SS inserts is possible to reduce the temperature in the low carbon steel turrets of the GSU transformer. This article demonstrates that by elongating and increasing the width of the original short SS inserts it is possible to reduce the temperature in the low carbon steel turrets of the GSU transformer. The magnetic solution presented in this article could be implemented on-site without the need to send the transformer to repair and avoid taking out of service the transformer for a long time

Temperature reduction in turrets - part I

This article presents the identification process of high temperatures in low voltage (LV) turrets of a single-phase generator step-up (GSU) transformer which is equipped with non-magnetic stainless steel (SS) inserts in the turrets. High temperatures are detected in the SS insert regions of the LV turrets utilizing thermography cameras and temperature labels. The presence of high temperature in the LV turrets generated issues in the transformer as the crystallization of the turret gasket seals and the presence of transformer oil leaks. To figure out the cause of the high temperature in the turrets, three-dimensional (3-D) finite element (FE) simulations are performed. Electromagnetic analyses coupled with thermal analyses are carried out to understand the origin of the high temperatures in the turrets of the GSU transformer. To validate the 3-D FE transformer model, the results of the FE simulations are compared with the temperature measurements in the turrets. With the FE simulation results, the author detected magnetic design issues related to the SS inserts and related to the magnetic material utilized in the turrets, which are producing high temperatures. The study presented could help transformer manufacturers to predict and prevent possible heating issues in GSU transformers in the LV turret regions

“EL ELEMENTO FINITO EN EL CONTROL DE LA SATURACIÓN MAGNÉTICA DE UN NÚCLEO TOROIDAL UTILIZANDO ENTREHIERRO VIRTUAL”

El objetivo principal de este trabajo es controlar las características de la curva de magnetización de un núcleo toroidal mediante el uso de un entrehierro virtual. Se utilizó el método del elemento finito ya que existe una compleja distribución del campo magnético y se emplea un material no lineal en el núcleo toroidal. Para realizar las simulaciones de elemento finito se propuso y se usó el programa comercial de elementos finitos ANSYS como herramienta para el estudio. Para analizar el comportamiento magnético del entrehierro virtual dentro del núcleo magnético toroidal se realizó un estudio magnetostático no lineal en dos dimensiones y se utilizó el método de Newton Raphson para resolver el problema. Mediante el uso de un entrehierro virtual se logró el control de las características de la curva de magnetización de un núcleo magnético toroidal realizando simulaciones de elemento finito variando la corriente de CD en los devanados de los agujeros para cada punto de la curva de magnetización; esto prueba que verdaderamente se crea un espacio de aire virtual por saturación magnética dentro del núcleo magnético toroidal, por lo tanto, se obtiene el mismo efecto con un entrehierro virtual que con un entrehierro físico. Se comprobó que un entrehierro virtual funciona igual que un entrehierro físico dentro de un núcleo toroidal. Se calculó la longitud del entrehierro físico que equivale a un entrehierro virtual creado por una cierta corriente de CD en los devanados de los agujeros dentro de un núcleo magnético toroidal y se hizo la simulación de elementos finitos del núcleo toroidal con su entrehierro físico equivalente y se comprobó que efectivamente funciona igual que un entrehierro virtual dentro del mismo núcleo. También se comprueba que se puede controlar el grado de saturación del entrehierro virtual mediante la intensidad de CD en los devanados de los agujeros. Además mediante algunas simulaciones de elemento finito se demostró que el tamaño del entrehierro virtual depende de la intensidad de CD en los devanados de los agujeros. Con los resultados obtenidos se concluye que al usar un entrehierro virtual se aprovechan todas las ventajas de los núcleos magnéticos con y sin entrehierros físicos. Los resultados aquí obtenidos abren la posibilidad de realizar varios trabajos en un futuro

Combined Propulsion and Levitation Control for Maglev/Hyperloop Systems Utilizing Asymmetric Double-Sided Linear Induction Motors

This article presents a new method for combined levitation and propulsion control in maglev/Hyperloop systems by selectively applying AC and DC modes of operation to a group of asymmetric double-sided linear induction motors (ADSLIMs). Although adjusting the AC current magnitude of lower and upper primary windings in ADSLIMs allows simultaneous control of thrust and lift forces, the limitation of this current balancing technique prohibits them from producing a high lift force while operating with low thrust force. To overcome this limitation and to simultaneously control the thrust and lift forces of the ADSLIMs with high efficiency under different operating conditions, a combination of AC and DC modes of operation is proposed. AC mode of operation consists of feeding different AC current amplitudes to the upper and lower ADSLIM primary windings to produce and control the required thrust and lift forces. The DC mode of operation consists of controlling one or several ADSLIMs to operate with DC excitation to realize the desired lift force at lower thrusts which otherwise cannot be achieved by operating in AC mode alone. The concept of the new combined control strategy is studied using two-dimensional finite element (FE) electromagnetic simulations and compared with an Inductrack permanent magnet (PM) based passive magnetic levitation system