Abstract
The method of thermal imaging inspection allowing detecting defects at an early stage of their development is considered. The essence of the method consists in recalculation of measured temperature drops into insulating characteristics measured under operating voltage. It is shown that defects are detected at the early stage of their development using the defect detection criterion (tgδmeas-tgδcalc). It is concluded that it is possible to abandon a number of traditional methods of testing with electrical equipment shutdown.