Electric Power Systems Research 81 (2011) 2015–2037 Contents lists available at ScienceDirect Electric Power Systems Research jou rn al h om epage: www.elsevier.com/locate/epsr General asset management model in the context of an electric utility: Application to power transformers Juan L. Velasquez-Contreras a,∗ , Miguel A. Sanz-Bobi b , Samuel Galceran Arellano a a Polytechnic University of Catalonia, Department of Electrical Engineering, Diagonal 647, 08028 Barcelona, Spain b Comillas Pontifical University, Institute for Research in Technology, IIT, Santa Cruz de Marcenado 26, 28015 Madrid, Spain a r t i c l e i n f o Article history: Received 4 March 2009 Received in revised form 24 March 2011 Accepted 19 June 2011 Available online 19 July 2011 Keywords: Asset management Power transformers Detection Diagnosis Failure rate Maintenance a b s t r a c t GAMMEU 1 constitutes an integrated approach that covers the different elements related to the asset management of power transformers in the environment of a utility. GAMMEU harmonizes and inter- relates all the relevant subsystems of the asset management that normally are studied as individual entities and not as a system. Concretely, GAMMEU consists of a platform for data integration, an intelligent system for detection and diagnosis of failures, a failure rate estimation model, a module of reliability analysis and an optimisation model for maintenance scheduling. In this work, a brief description of the elements of GAMMEU is presented and the implementation of the intelligent system for detection and diagnosis as well as the failure rate estimation model is exemplified using data of measurements performed in real power transformers. A robust anomaly detection module using prediction models based on artificial intelligence techniques was developed for top oil temperature monitoring and the use of decision trees as classifiers for the assessment of FRA 2 measurements is also illustrated. For failure rate estimation, the use of a model based on hidden Markov chains is presented using data of dissolved gas analysis tests. The experience obtained from the implementation of part of the modules of GAMMEU using real data has demonstrated its feasibility. © 2011 Elsevier B.V. All rights reserved. 1. Introduction As a consequence of liberalization, investments in new trans- mission equipment have significantly declined over the past 15 years. Many transformers are working well beyond their intended life and are operating under increasing stress. As load is increasing, new generation, and economically motivated transmission flows push equipment beyond nameplate limits. As a result, business in the electrical sector has dramatically changed and for this reason, it is imperative to look for new opportunities and strategies for allowing electric utilities to survive these changes. In order to counterattack the undesirable consequences of the previously mentioned factors, utilities have looked for new meth- ods and strategies that allow not only to achieve determined levels of reliability but also to do it in the most cost-effective manner. Among the different controllable elements that directly affect the network reliability, maintenance is the one of major relevance. ∗ Corresponding author. Tel.: +34 93 401 67 27; fax: +34 93 401 74 33. E-mail addresses: juanlorenzovc2000@yahoo.es (J.L. Velasquez-Contreras), masanz@upcomillas.es (M.A. Sanz-Bobi), galceran@citcea.upc.edu (S. Galceran Arellano). 1 GAMMEU: general asset management model for an electric utility. 2 Frequency response analysis. Between maintenance and reliability there is a clear relationship. If the equipment is not maintained, the probability of failure occur- rence will increase, while in the case that the equipment is well maintained, it will be lower, but of course, at higher maintenance costs. In this sense, equilibrium between reliability and mainte- nance expenditure is required. As indicated in [1], the present state-of-the-art in maintenance strategies offers new opportunities which are structured in at least three basic approaches for making decisions related to mainte- nance. These opportunities are: (1) condition-based maintenance (CBM); 2) reliability centred maintenance (RCM); and (3) optimi- sation techniques (asset management/Risk Management). Ref. [2] presents an interesting work that shows the experi- ence in Germany regarding the application of the RCM-strategy. By determining both condition and importance criteria, the strat- egy allows for determining which equipment has to be maintained first. It is worth mentioning the existence of a commercially avail- able tool that works using this strategy [3]. Most of the authors who have written about this subject give positive opinions with regard to the implementation of the RCM strategy through condition and importance indices. Nevertheless, there are also some sceptical works, as the one indicated in [4], where it is stated that the imple- mentation of RCM programs in this way represents a significant step in the direction of “getting the most out” of the equipment installed. However, the approach is still heuristic, and its applica- 0378-7796/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.epsr.2011.06.007