Comparison of maintenance scheme effects on power transformer reliability performance
Authors: Duran Tovar Ivan Camilo , Rosero Zuñiga Laura Sofia , Pavas Martínez Andrés , Duarte Velasco Oscar Germán 
Published: November 2015

<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>