Int. J. Reliability and Safety, Vol. 1, No. 4, 2007 513 Copyright © 2007 Inderscience Enterprises Ltd. An interval computation approach for power components overload protection in the presence of data uncertainty Alfredo Vaccaro* and Domenico Villacci Dipartimento di Ingegneria, Power Systems Research Group, Università degli Studi del Sannio, Piazza Roma 21, Benevento I82100, Italy E-mail: vaccaro@unisannio.it E-mail: villacci@unisannio.it *Corresponding author Abstract: The embedding of microprocessor-based relays in power components enables improved overload protection because of higher computational resources, adaptiveness and flexibility. The increased computing power that is now embedded in power component devices makes possible the real-time simulation of built-in thermal models. However, the use of model-based protective systems is exposed to the uncertainty affecting some model components. The effect of these uncertainties could compromise the overall protective function reliability. To address this problem, we use Affine Arithmetic (AA). In particular, AA can be used to calculate the component’s hot spot temperature by solving a thermal dynamic model where parameters are imprecise, and the uncertainty is represented by affine forms. The proposed solution method is implemented on a microcontroller-based unit to develop a prototype thermal relay equipped with robust tools for uncertainty data management. Various experimental results are presented and discussed. Keywords: overload protection; interval computing; uncertainty representation; Affine Arithmetic; AA. Reference to this paper should be made as follows: Vaccaro, A. and Villacci, D. (2007) ‘An interval computation approach for power components overload protection in the presence of data uncertainty’, Int. J. Reliability and Safety, Vol. 1, No. 4, pp.513–531. Biographical notes: Alfredo Vaccaro received an MSc in Electronic Engineering in 1998 from the University of Salerno. He was an Assistant Researcher at the University of Salerno, Department of Electrical and Electronic Engineering from 1999 to 2002. Since March 2002, he has been a Research Scientist and aggregate Professor in Electric Power Systems at the Department of Engineering of University of Sannio. His special fields of interest included soft computing and interval-based method applied to power system analysis and advanced control architectures for diagnostic and protection of distribution networks. He is a Member of IEEE and a Member of the Editorial Boards of the IET Renewable Power Generation, the International Journal of Electrical and Power Engineering, the International Journal of Reliability and Safety and the International Journal of Soft Computing.