A Tool for estimating remaining life time of a power transformer

Abstract

Power transformers are vital assets in electric power systems, as they are essential in maintaining a reliable supply and very high in cost. Nowadays, society has become more and more dependent on the availability of power, putting pressure on the reliability, availability and cost efficiency of power supply. These assets operate under high electric stresses and although transformers are extremely energy efficient, the dissipated heat is a limiting factor for the maximum loading of power transformers. The insulating medium must be capable of dealing with large electric stresses, strong electro-mechanical forces and high temperatures. The life of a power transformer mainly depends on the condition of the paper-oil insulation system. Manufacturers often define the expected life of power transformers to be between 25 and 40 years. Some transformers in service are now approaching this age, and it is important to estimate their remaining lifetime in order to prevent premature shutdown of transformers. Knowing the condition of the transformers is an essential factor to make an economical decision for transformer replacement and maintenances. This paper presents a mathematical model to estimate the remaining life through assessment of furfural content in the oil and degree of polymerization of the insulating paper.