WHITEPAPER: Overview Factors on Assessing Insulation Life

The failure of power transformers is always an area of significant concern since it can result in millions of dollars in costs, interruption of power and as well as possible environmental and safety impacts. Therefore, it is desirable to detect the existence of abnormal changes in the transformer's internal condition and being able to diagnostic if this could be an incipient failure. Active detection of incipient faults is now possible through on-line monitoring of abnormal changes in some parameters and the use of diagnostics methods provide an assessment of equipment condition and suggested actions. When everything seems to be normal and end of life depends only on the insulation life there are some parameters and their records that seem to be overview when assessing the transformer insulation life. Winding hottest spot temperatures, moisture, oxygen, oil aging products and particles of different origin are agents of degradation that can shorten transformer life significantly under impact of thermal, electric, electromagnetic and electrodynamics stresses. This paper gives an overview of the status of determination of the winding hottest spot and moisture in insulation as well as recommendations to obtain and maintain these records.