Continuous monitoring systems for power equipment have become more and more widespread in recent years, due to a number of reasons. First of all, this is determined by a significant aging of the power equipment park, which leads to a decrease in its operational reliability. Indeed, to maintain the required reliability, “old” equipment requires much more attention and especially a significant reduction in the period of its monitoring. The digitalization of the industry plays a significant role in this process. Digitalization is impossible without the use of the latest technologies, which include continuous monitoring of equipment. In addition, digitalization implies a reduction in the human factor in operation based on the wider use of computer technology. To the greatest extent, all this applies to transformer equipment. Systems for continuous monitoring of transformer equipment began to be used in the late 80s and by now, considerable experience has been accumulated in their development and operation. The paper analyses the basic principles of constructing systems for continuous monitoring of power transformers of higher voltage classes, shows the need to use them, especially for transformers with a long service life, defines the requirements for these systems, gives the parameters that need to be monitored by these systems. As an example of a continuous monitoring system, the authors describe SKIT system developed at Peter the Great St. Petersburg Polytechnic University. SKIT has been introduced and is being commercialized at a number of energy facilities.