Transformer Sustainment Investment Options

Abstract

Large power transformers are used extensively in power systems to facilitate economic long distance transmission of power, transforming it to higher voltage levels at generation sites and then transforming it to lower levels near load centers. Transformers represent one of the most significant asset investments for most utilities. Transformers are manufactured carefully according to tight specifications and are carefully operated and maintained in service. However, the materials used in transformers age and lose mechanical and electrical strength and they will eventually fail in service unless action to sustain them is taken. Utilities have several sustainment options. This chapter discusses two of these. The first is to invest in diagnostic monitoring systems, while the second is to invest in a major mid-life refurbishment. The diagnostic monitoring option is typically of interest for transformers considered to be near end-of-life in service as a generator step-up transformer, auto transformer, or a transformer serving a critical load. Mid-life refurbishment is more widely applicable, for transformers have been in service for perhaps 20–30 years depending on the application.

Consideration of these types of options might be included in near-term asset management decision-making for a relatively few specific assets as a part of Operational Asset Management function as discussed in Chap. 6 of Part 1, or to form the basis for broader company policies for transformer fleets as a Tactical Asset Management function as discussed in Chap. 7 of Part 1.

This chapter starts with examples and case studies for investment in diagnostic monitoring and for mid-life refurbishment from earlier CIGRE technical brochures and session papers. These case studies are extended and updated using the risk-based business case analysis methods of Chap. 8 Part 1, to produce results useful for guiding investment decision-making.