This paper shows the results obtained from the simulated study case about the impact of harmonics on a distribution transformer useful life. These results depend on the supplied energy level (power variation along the time) under three different demand profiles with the same harmonics level. It will be presented that the transformer overload affects the transformer useful life subjected to the presence of peaks and valleys in the weekly demand profile, providing period times to the transformer for the temperature increase (peaks) or decrease (valleys). These temperature variations will affect directly the transformer loss of life and will show that not only the harmonic presence on the transformer operation will accelerate its aging, but also other conditions allow a slow aging and even a useful life beyond the rated expectation. The possible effects of more complex disturbing scenarios, like unbalanced currents and high reactive power feeding, are presented as discussion.

Este artículo presenta una aproximación al análisis de estabilidad del ángulo del rotor de un sistema máquina-barra Infinita. Se analiza la estabilidad del ángulo del rotor de un sistema típico máquina-barra infinita, bajo determinadas condiciones de operación. Posteriormente se incorpora un estabilizador de sistema de potencia para lograr un amortiguamiento en el modo mecánico que permita mantener un sincronismo en su operación. Finalmente, se presentan los resultados con simulaciones realizadas con la herramienta computacional Matlab®.

El presente artículo pertenece al desarrollo del proyecto de grado “Diseño y Construcción de una Turbina Hidráulica de 3 Kw".

No abstract

<span style="font-family: OptimaLTStd; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;">Power transformer failures have a significant impact on electrical systems reliability, as they compromise the electricity delivery. Failures <span style="font-family: OptimaLTStd; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;">impact the operational cost of electric utilities as they endanger the accomplishment of power commitments. Power transformer <span style="font-family: OptimaLTStd; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;">failure rate can be modeled from its health condition, which is determined from different condition parameters. This paper is aimed <span style="font-family: OptimaLTStd; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;">to compare different maintenance schemes that allow the asset to be available the longest possible time. The power transformer <span style="font-family: OptimaLTStd; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;">operation is represented considering actual electric load profiles and temperature. Electrical and thermal transformer parameters are <span style="font-family: OptimaLTStd; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;">taken from manufacturer tests and technical standards. An electrical-thermal model is employed to estimate the life span reduction <span style="font-family: OptimaLTStd; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;">and temperature changes. From life span and loading, the health condition is determined, so as the effects of different maintenance <span style="font-family: OptimaLTStd; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;">schemes. The failure rates are calculated for unmaintained conditions and different maintained schemes, allowing to determine their <span style="font-family: OptimaLTStd; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;">effects on transformer reliability. Optimal maintenance schemes are determined and the expected benefits in failure rate reduction, <span style="font-family: OptimaLTStd; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;">asset reliability and life span extension are presented. As a result, it was found that certain time-based maintenance schemes provide <span style="font-family: OptimaLTStd; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;">better transformer reliability performance in comparison to condition based schemes,  allowing to reduce the interruptions and<br /><span style="font-family: OptimaLTStd; font-size: 9pt; color: #231f20; font-style: normal; font-variant: normal;">extending the life of the transformer.</span></span></span></span></span></span></span></span></span></span></span><br style="font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px;" /><br class="Apple-interchange-newline" /></span>