STRATEGIES TO REPLACE, REFURBISH, REPAIR AND UPGRADE POWER TRANSFORMERS: THE SPANISH EXPERIENCE.

摘要

Different strategies to replace, repair, refurbish and upgrade power transformers and the Spanish experience in this field are presented, covering both high voltage transmission and generator step up applications. Those include repair and refurbishment operations on site and in manufacturing facilities, the alternative to replace windings of existing units to increase the power output and to reduce load losses, the use of standardized units, universal transformers and multi-voltage poly-transformers for contingency planning and the progressive re-powering on site of the main transformers in a nuclear power plant. When deciding the best alternative to replace, refurbish or repair a transformer, several factors need to be considered, especially the cost and time to accomplish the work, but also the kind of defect or fault, the age and type of transformer, the possible technical alternatives and the associated risks. Refurbish or retrofit a transformer provides cost advantages related to reusing existing materials. Some retrofit and repair examples are presented including change of windings with the benefit of reutilization of the core and tank. The repair of a power transformer in a manufacturing facility is a good alternative, especially when the dimensions and weight allow transportation by road, implying a quick and reasonable cost solution for shipment. Performing on site repair works is a different option with similar reliable and quality results, requiring an adequate preparation and conditioning of the environment, special equipment, processes, testing and experienced personnel. The main advantages related to on site repair works are shorter repair time and lower cost when compared to shipment to a repair location, especially for bigger size transformers. The circumstances existing in each particular case will determine the optimum alternative but an adequate contingency planning and a proper policy of spares, considering the strategic importance and risk of the transformer, simplify the decision process and help to achieve satisfactory results, minimizing the cost and time of unavailability.