Thermal Expansion of RIP/RIS Material : Creation of a thermal-chemical-mechanical simulation model to study thermal displacement of materials

Sammanfattning

During the curing of an epoxy based insulation material in high voltage bushings, coupledthermal, chemical and mechanical phenomena occur which have a significant effect on the finaldeformation and structure of the system. The purposeofthis study is to build up anumerical modelusing COMSOL Multiphysics simulation software to simulate the thermomechanical response ofresin impregnated paper (RIP) and resin impregnated synthetic (RIS) insulation during curing.The model includes heat transfer and internal heat generation, cure kinetics and mechanicaldeformation, such as thermal expansion and chemical shrinkage. The properties of the materialare temperature and degree of cure dependent, while the multi-component core structure isrepresented using a homogenization approach.Multiple heating zones are used to achieve time-dependent temperature profiles, to model realisticcuring conditions. It is seen from the simulation results that the heat generation due to exothermicreaction strongly influences the evolution of temperature and results in non-uniform temperaturedistribution in the core. The extent of cure is not uniform, and is found to be less in areas of lowertemperature exposure. Thus, the internal stresses and measurable displacement generated in theinsulation structure are a result of non-uniform thermal expansion and chemical shrinkage. Themodel shows that deformation behavior highly depends upon the curing conditions, and it can beusedasa guideline to optimize temperature profiles to minimize the displacement and dimensionalinstability in high voltage bushings.