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The paper is concerned with the importance of investigating the influence of the operation life of transformers on their energy characteristics. This problem is really pressing for all the network transformers of the PJSC “Magnitogorsk Iron and Steel Works” (PJSC “MMK”) as a significant number of them have been in operation for 50 years of even longer. The literature review carried out by the research group revealed that in most cases the information about energy characteristics and about the transformer efficiency is obtained from the calculations based on the certified values of the idling losses and short-circuit losses. The research group noted the efficiency of experimental determination of the transformer efficiency on the basis of the idling losses and short-circuit losses. An experiment was carried out to calculate electric losses by power measurement using the two-wattmeter method. The connection diagram of the measuring device was considered. The assessment was given to the influence of the power measurement accuracy on the calculation of the transformer efficiency, which has been in operation for more than 60 years. The results of experimental data processing are presented. The investigations confirmed the insignificant increase of iron losses and the decrease of the transformer performance by about 0.5%. This confirms the possibility of making use of transformers for longer periods then the normative period if timely maintenance work and scheduled repairs are provided. The authors carried out the analysis of the obtained results and compared them with the materials published by other scientists. They stressed the need to take into account the increase in iron losses when the service life exceeds 20 years. The paper also provides recommendations on improving of the maintenance service by means of installation of on-line state monitoring systems.


Power transformer, service life, performance, electric losses, experiment, literature review, statistics, maintenance service, on-line monitoring, recommendations.

Nikolay N. Druzhinin

Production engineer, Central electro-technical laboratory, PJSC «Magnitogorsk Iron and Steel Works», Magnitogorsk, Russia. E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

Artur A. Sarlybaev

Ph.D. (Engineering), Manager of the planning and reliability department, Steel Service-2 shop, United Service Company LLC, Magnitogorsk, Russia. E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

Ekaterina A. Khramshina

Research officer, Nosov Magnitogorsk State Technical University, Magnitogorsk, Russia.

Olga I. Karandaeva

Ph.D. (Engineering), Research officer, South-Ural State University, Chelyabinsk, Russia.

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