School of Electronics and Information, Xi'an Polytechnic University, Xi'an 710048, China.
State Key Laboratory of Electrical Insulation and Power Equipment, Xi'an Jiaotong University, Xi'an 710049, China.
Molecules. 2023 Jan 20;28(3):1067. doi: 10.3390/molecules28031067.
Insulating oil plays a crucial role in internal insulation of oil-impregnated transformers. It has been demonstrated in a variety of experimental studies that mineral oil (MO) and vegetable oil (VO) can be blended in different ratios to improve insulation properties; however, the mechanisms underlying this phenomenon remain unclear. In this study, a molecular dynamics (MD) simulation approach was used to investigate diffusion of water molecules in VO/MO blends and dielectric constants of a mixture. The results show that the diffusion coefficient of water molecules is negatively correlated with the proportion of VO; thus, addition of VO helps to improve the insulation properties of a mixture. Due to introduction of strong polar functional groups, a decrease in the diffusion behavior of water molecules can be attributed to an increase in the interaction energy and formation of hydrogen bonds between water molecules and the mixed oil system. There is a direct correlation between the dielectric constant of a mixture and VO content; however, it is very sensitive to water content. The presence of strong polar water molecules or functional groups in a mixture leads to an increase in the dielectric constant, which results in a reduction in insulating properties. Accordingly, presence of polar groups plays an important role in determining the insulating properties of a mixture. To increase the insulation performance of a mixture, it is important to consider the diffusion-inhibiting and dielectric effects of the stronger polar groups in vegetable oil compared to those in mineral oil.
绝缘油在油浸式变压器内部绝缘中起着至关重要的作用。在各种实验研究中已经证明，矿物油 (MO) 和植物油 (VO) 可以以不同的比例混合，以提高绝缘性能；然而，这种现象的机制尚不清楚。在这项研究中，采用分子动力学 (MD) 模拟方法研究了水分子在 VO/MO 混合物中的扩散和混合物的介电常数。结果表明，水分子的扩散系数与 VO 的比例呈负相关；因此，添加 VO 有助于提高混合物的绝缘性能。由于引入了强极性官能团，水分子的扩散行为减少可以归因于水分子和混合油系统之间的相互作用能增加和氢键形成。混合物的介电常数与 VO 含量呈直接相关，但对含水量非常敏感。混合物中存在强极性水分子或官能团会导致介电常数增加，从而降低绝缘性能。因此，极性基团的存在在确定混合物的绝缘性能方面起着重要作用。为了提高混合物的绝缘性能，必须考虑到植物油中较强极性基团的扩散抑制和介电效应与矿物油相比的差异。
