Abstract
To study the microscopic thermal aging mechanism of insulating paper cellulose through molecular dynamics simulation, it is important to select suitable DP (Degree of Polymerization) and force field for the cellulose model to shorten the simulation time and obtain correct and objective simulation results. Here, the variation of the mechanical properties and solubility parameters of models with different polymerization degrees and force fields were analyzed. Numerous cellulose models with different polymerization degrees were constructed to determine the relative optimal force field from the perspectives of the similarity of the density of cellulose models in equilibrium to the actual cellulose density, and the volatility and repeatability of the mechanical properties of the models through the selection of a stable polymerization degree using the two force fields. The results showed that when the polymerization degree was more than or equal to 10, the mechanical properties and solubility of cellulose models with the COMPASS (Condensed-phase Optimized Molecular Potential for Atomistic Simulation Studies) and PCFF (Polymer Consistent Force Field) force fields were in steady states. The steady-state density of the cellulose model using the COMPASS force field was closer to the actual density of cellulose. Thus, the COMPASS force field is favorable for molecular dynamics simulation of amorphous cellulose.
Highlights
Oil-paper insulation is the main form of insulation for large power transformers
Because there have been few studies on the selection of the optimal polymerization degree and force field in the molecular dynamics simulation of insulating paper cellulose, a large number of models are considered in this paper
The cellulose models were constructed using Materials Studio software (Accelrys, San Diego, pressure intensity was set as 0.2 GPa, the Berendsen method [23] was used as the control method, CA, USA)
Summary
Oil-paper insulation is the main form of insulation for large power transformers. Cellulose is an important component of insulating paper; the properties of cellulose decide the properties of insulating paper, and the service life of transformers. Especially of insulating paper cellulose, the selection of the polymerization degree and force field of the calculation model is very important to obtain correct simulation results and shorten the simulation time. Further studies are required to confirm how to select a relative appropriate polymerization degree of the cellulose model used in molecular dynamics simulation to reflect the actual basic characteristics of cellulose and minimize the time of analog simulation. Similar to the case for the selection of the polymerization degree, further studies are required to confirm which force field should be selected to reflect the actual basic characteristics of cellulose to obtain more accurate simulation results. Because there have been few studies on the selection of the optimal polymerization degree and force field in the molecular dynamics simulation of insulating paper cellulose, a large number of models are considered in this paper. The relative optimal force field was determined from the perspectives of the degree of closeness between the steady-state density of the cellulose model and the actual cellulose density, volatility, and repeatability of the mechanical properties of the model
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