Modern practice of the development of technical systems, and electrical engineering in particular, shows that their reliability is laid at the design stage and is ensured at the stage of production. The imperfection of production technology and viola-tion of operating modes can lead to the appearance of various defects in the finished systems. Thus, the diagnosis of a technicalob-ject (system) must necessarily be present at all stages of its life cycle.Therefore, various workson ensuring the process of diagnosing the technical system is carried out in its design, manufacturing, testing and operation. At the same time, the purpose of the diagnosis is to maintain the necessary level of indicators of the technical state of the system. At the design stage, the main task of diagnosing is to provide the possibility of a potential diagnosis of the system being designed, and at the stage of production and operation, the current control of its performance.The constant increase in the complexity of technical systems, due to the increase and complica-tion of the functions performed, the improvement of production technology, the increase ofrequirements to quality indicators, etc., leads to the complication of methods and diagnostic tools that provide the necessary properties of systemsFor the diagnosis of elec-trical devices, methods such as: peripheral scanning, automatic generation of samples, built-in self-scanning, as well as methods of parametric identification, fault control methods, evaluation methods, etc. are used. Many of these methods are characterized by the following disadvantages: significant amount of computations, the need toaccess all nodes of the electrical circuit, the sensitivity to the errors of the calculations, and, as a consequence, the complexity of practical implementation. In addition, a significant spread in the diagnosis of electrical devices acquired a method ofreference, based on the finding of a set of values of voltages or currents at the control points of those of them closest to the values obtained during measurement in the device being diagnosed.Despite the considerable achievements in the field of diagnosing the technical state of the systems, the relevance of theoretical research and the practical application of diagnostic methods as the basic principles for ensuring the necessary quality indicators of systems (and elec-trotechnical, in particular) and increasing the reliability of estimates of the technical condition of the latter remains determinative at the present time.Conditions of independent monitoring and control are considered and investigated, which ensure the possibility of conducting a diagnostic experiment without the withdrawal of a controlled system from operation.