No abstract

At present it is claimed that all electrical energy systems operate with high values of efficiency and reliability. In electric power systems (EPS), electrical power and distribution transformers are responsible for transferring the electrical energy from power stations up to the load centers. Consequently, it is mandatory to design transformers that possess the highest efficiency and reliability possible. Considerable power losses and hotspots may exist in the bushing region of a transformer, where conductors pass through the tank. Most transformer tanks are made of low-carbon steel, for economical reasons, causing the induction of high eddy currents in the bushing regions. Using a non-magnetic insert in the transformer tank can reduce the eddy currents in the region and as a consequence avoid overheating. In this work, analytical formulations were developed to calculate the magnetic field distribution and the stray losses in the transformer region where bushings are mounted, considering a stainless steel insert (SSI) in the transformer tank. Previously, this problem had only been tackled with numerical models. Several cases were analyzed considering different non-magnetic insert sizes. Additionally, a numerical study using a two dimensional (2D) finite element (FE) axisymmetric model was carried out in order to validate the analytical results. The solved cases show a great concordance between models, obtaining relative errors between the solutions of less than two percent.

No abstract

Fundamental parts of an electrical system are radial systems, which may be operating at different voltage levels, where an unwanted event such as ferroresonance is possible to occur. The conditions for the presence of a ferroresonance in an electrical system can present high overvoltages that can result in damage to critical equipment, high costs of corrective maintenance and plant shutdowns. These impacts mentioned justify the importance of analyzing, predicting and being able to establish strategies that avoid ferroresonance. In the present work simulations of radial feeders are shown where the ferroresonance event is presented as well as strategies to mitigate it by observing the behavior of voltage signals through simulations in the ATPDraw software.