6. Non-electrical Diagnostic Methods

Already from the titles of the paragraphs of this chapter, we can conclude that the progress of recent decades in the field of non-destructive testing of a wide range of products and materials has given power engineers a large number of various reliable methods and means of monitoring the state of high-voltage equipment of electric power systems. Some of them have been used by power engineers for many decades and continue to improve them, others have been developed relatively recently, and specialists strive to fully use their potential. For the diagnostics of oil-filled equipment, the leading place belongs to the methods of chemical control of the state of insulating liquids, to control the state of the insulating structures of overhead power lines and open substations—methods based on the registration of electromagnetic radiation of various frequency ranges.