Study of Thermal and Electrical Aging in Epoxy Resin through Electroluminescence Measurement

The reliability of HVDC systems is largely dependent on the performance of the insulation under high electric fields. Solid polymers or their composites, often used in insulation, are subject to multiple stresses throughout their lifetime. Prolonged exposure to thermal, electrical and environmental factors results in aging; resultant modifications to material microstructure causes progressive insulation degradation. In this work, Electroluminescence (EL) measurements using a photomultiplier tube (PMT), working in photon counting mode, is used as a diagnostic tool to study space charge dynamics with aging of material. The material considered is epoxy resin due to its prevalence in high voltage insulation. The specimen is subjected successively to thermal and electrical aging. Electroluminescence (EL) measurements are performed before and after aging. The variation of EL with field and temperature of aging is studied. Electroluminescence increases with field in both unaged and aged samples. Electroluminescence intensity decreases with aging, both electrical as well as thermal.