The transformer is one of the key inventions for the development of humanity. It has enabled us to transmit electrical energy over very long distances. Electrical energy is crucial for human development, especially in reducing physical labor, creating new jobs, and improving the standard of living. The great inventor Nikola Tesla utilized his invention of the induction motor for the further advancement of transformers. Today, we cannot imagine the world without transformers. They are built with power ranging from a few watts to massive capacities of 360 MW. These significant power differences demonstrate that transformers are used nearly everywhere. Operating voltages range from 3.5 V to voltages of 420 kV and higher. There are various types of transformers: auto-transformers, insulation transformers, rotary transformers, measuring transformers, and more. The goal of this final paper is to engage readers and stimulate thoughts on the importance of transformers in today's world. To demonstrate and explain the significance of maintenance and testing (revision) of transformer stations. Key aspects include maintaining its insulation and measuring temperature changes during its operation. Special attention must be paid to oil insulation, which must be continuously monitored. Today, the world is increasingly shifting towards environmentally friendly energy sources, such as electrical energy. This accelerates the production and installation of transformers. Increased interest urges us to better educate ourselves about the operation of transformers and familiarize ourselves with measures for their maintenance because the main goal of maintenance is to minimize breakdowns, downtime, and extend product lifespans.