Using characteristics of magnetic fields as diagnostic parameters is due to their direct interconnection with energy conversion processes, structural and functional features of electric power equipment, current state and modes of its operation. The cumulative effects on the diagnostic parameter lead to changes in its value, and their diversity causes differences in the nature of these changes. Analysis of the nature of these changes is used to describe diagnostic signs associated with the exposure of faults, which provides greater efficiency in detecting early signs of deviations from the normal state and greater selectivity in case of multiple faults. At the same time, monitoring of external magnetic fields of electric power equipment in various areas of their occurrence-temporal, spatial and frequency-is implemented without the objects destructing, changing the technological process or modes of their operation. The aim of the work is to develop principles of construction and operation, methods for implementing a set of tools for studying electric power equipment through continuous or periodic monitoring of magnetic fields and the use of monitoring results in technical diagnostics systems. Summary: 1. A multi-level functional specification of a system has been developed, which is implemented by its hardware and software components; 2. The choice of primary measuring transducers is