Rationale for the need to develop strategies for replacing 6-10/0.4 kV power transformers in electric grid companies

This article provides a comprehensive analysis of scientific papers, regulatory documents, and practical research on the operation, optimization, and replacement criteria of 6-10/0.4 kV power transformers in the Russian Federation's electric grid. The analysis identified key factors affecting transformer performance: operational irregularities, overload and underload conditions, as well as equipment wear and tear. Using the Oryol district of the Oryolenergo branch of PJSC Rosseti Centre as an example, an assessment of the operational condition of the transformer fleet was conducted. It revealed that 74% of the surveyed transformers operate with a load factor of no more than 20%, leading to increased energy losses and reduced power supply reliability. The impact of winding connection schemes on the operating parameters of 6-10/0.4 kV transformers was also examined, and the developed technical refurbishment strategy, which provides for annual equipment replacement, was analyzed. It was found that the greatest technical and economic benefits are achieved by replacing transformers with rated capacities of 63, 400, and 630 kVA. Particular attention was also paid to the implementation of new energy-efficient transformers and digital monitoring systems, which improve the efficiency and manageability of network equipment. The analysis revealed that existing research and proposed solutions cover specific aspects of energy efficiency improvement, including load optimization, improved winding connection schemes, the use of energyefficient transformer classes, and the digitalization of control and metering processes. However, a unified strategy is lacking, necessitating the development of a comprehensive strategy for the modernization and replacement of 6–10/0.4 kV power transformers. This strategy will serve as the foundation for the long-term development of the electric grid complex, ensuring a balance between reliability, cost-effectiveness, and energy efficiency.