Technical diagnostics has a strong position in the global engineering community. It is included in the standards and recommendations for both existing and projected nuclear power plants. All foreign operating nuclear power plants are more or less equipped with means of technical diagnostics of reactor installations either from the very beginning or during modernization. Regardless of the diagnostic architecture of the automated control system, whether it is Framatom's local project systems or Westinghouse's centralized systems, diagnostic algorithms are universal. The operating organization of Rosenergoatom Concern JSC pays great attention to the development of technical diagnostics tools. Over the past 20 years, almost all Russian power units have been equipped. This contributed both to improving the safety of operation, and ensuring reliability, and extending the life of existing nuclear power plants. The article presents the authors' classification of technical diagnostics systems, the features of their operation at the Novovoronezh NPP site for a 30-year period of time. Complex, high-tech diagnostic systems are moving into operational practice with great difficulty and skepticism. The systems are slowly being filled with diagnostic knowledge, but our demanding foreign customer will undoubtedly require this diagnostic knowledge.