OPTIMIZATION OF POWER TRANSFORMERS WITH GRADED INSULATION

The insulation system plays a key role in the safe and reliable operation of all electrical machines, especially when it comes to power transformers. It is designed to ensure the durability of the transformer against dielectric and thermal stresses under various ambient and operating conditions. The design of the insulation system is one of the most important engineering aspects in the production of transformers, especially in the case of high–voltage power transformers. By following adequate procedures, as well as calculations and analyses, the use of suitable insulation materials, controlled production processes ensure the quality and reliability of the transformer, and the robustness of the insulation system is necessary for a smooth and long operating life of the transformer. Comprehensive verification of sizing rules is essential to increase reliability, as well as to optimize material costs, which opens the topic of optimization possibilities depending on the technical requirements for insulation parameters, all in accordance with the requirements of the Investor. The focus of the work is on power transformers with a voltage level of 110kV where the high–voltage connection is realized in „YN“ coupling, which is almost always the case when observing the units installed on the territory of the Republic of Serbia. An analysis of the insulation details of the 110kV connection in the variation with uniform insulation and graded insulation is foreseen, as well as the influence of this parameter on the dimensions, and therefore on the price of the final product. As the requirements for the insulation level of power transformer connections and corresponding dielectric tests are an input parameter in the design annex, that is, part of the technical specification of the Client, part of the work is also intended to consider the essential need for full insulation of 110kV connections. The idea is for this chapter to be the starting point for creating new works on this topic from the point of view of operators of distribution and transmission networks. The aim of the work is to review the possible points for optimizing the power transformer using graded insulation instead of uniform insulation of the high–voltage terminal, as well as opening new discussions on this topic from the point of view of transformer manufacturers, operators of distribution / transmission networks and, of course, end users.