A Multi-dimensional ModeltoDescribe theAgeing Process inPolymers UsedforElectrical Insulation

A lotofknowledge onthebehaviour of polymers usedaselectrical insulators hasbeenacquired overthelast decades. Themajordifference inlife models describing theelectrical ageing process inthese materials isbasedon thecauseinitiating the degradation. Therole ofspace charges asaprimary step orconsequence ofageing became contradictory factors. However,most of thesemodelsrelyon a thermodynamical approach. Theageing process is assumed tobedominated bya single reaction that involves theinitial state andthefinal state. A "double wellpotential" representation issystematically provided bytheauthors todescribe thefree energy variation and themoiety transfer inthesystemduring theageing process. Inourbibliographical study, wehavenotyet foundanentirely reliable modelwhichtakesinto consideration thedistribution ofthefunctions inthe molecular mobility ofpolymer chains. Itiswellknown thatpolymers present asocalled energy distribution function. Themaininterest ofthisanalysis isthe possibility tointegrate thedistribution function concept associated withthebarrier energies inelectrical insulators life models.