Reactive Molecular Dynamics Simulation of Transformer Oil Pyrolysis Based on ReaxFF Reactive Force Field

Fast pyrolysis of transformer oil occurs at local high temperature caused by internal fault in power transformers and this may lead to transformer insulation deterioration. Because numerous subjects such as electrical, material and chemistry are involved and further research of microcosmic reaction mechanism is limited. In this paper ReaxFF reactive force field in which atom connectivity is presented by bond order is introduced to carry out reactive molecular dynamics simulation for transformer oil molecular models and their pyrolysis mechanism at high temperature are investigate. Alkanes C 16 H 34 , cycloalkanes C 16 H 30 and aromatic hydrocarbons C 16 H 18 with the same C atoms number 16 are taken as transformer oil examples and initiation pyrolysis mechanism, molecular interaction and products distribution during the whole process for different types of molecules at high temperature are simulated based on ReaxFF reactive force field reactive molecular dynamics. The results indicate that the pyrolysis of these three molecules is similar, the unimolecular dissociation is the main pathway at the early stage of pyrolysis while at the later period it is intermolecular radicals interaction dominated; the final products are mainly small hydrocarbons and radicals, such as C 2 H 4 , C 3 H 6 , CH 4 , H 2 , C 2 H 6 , C 3 H 4 , while most of the large hydrocarbons and radicals whose C atoms more than 6 mainly serve as intermediate products and decompose into small hydrocarbons and radicals with reactions going on. The difference is that the saturation of generated small molecule hydrocarbon increases for C 16 H 34 , C 16 H 30 and C 16 H 18.