The main goal of the project is to design and develop a diagnostic system for condition monitoring of HV el. machines. The system will allow to monitor and evaluate the level of partial discharge produced at DC and low-frequency power supply voltage to determine the current state of the winding insulation system. This diagnostic method is currently known in theory, however, has not found wide application in practice. On the market of such diagnostic systems, nobody offers a similar diagnostic system despite it holds the high potential "cheap" diagnose smaller HV el.