Atomic Scale Analysis of Water Motion Behavior in Three-element Mixed Insulation Oil Under Electric Field Stress

The motion behaviors of water in three-element mixed insulation oil (T-EMIO) were studied using mineral oil (MO) as reference by molecular simulation method. By analyzing the motion behavior, motion trajectory and interaction of water and insulating oil on atomic scale, the differences of motion behavior of water in different insulating oils were revealed. When the applied electrical field does not exist, H atom in water can form hydrogen bond with oxygen atoms in T-EMIO, resulting in strong interaction between water and T-EMIO. However, MO does not contain oxygen atoms and the Hydrogen atom s in MO cannot form hydrogen bonds with the oxygen atoms in water. In addition, the free volume (FV) fraction MO is bigger than T-EMIO. In this case, the mobility of water in MO is much greater than in T-EMIO. When the applied electrical field is present and enhances step by step, the interaction between water and T-EMIO decreases and the FV fraction of water in T-EMIO increases gradually. The interaction between water and MO becomes stronger and the FV fraction of water in MO is basically unchanged. Therefore, the motion capacity of water in the two insulating oils is basically the same under electrical field. This article provides professional support for the fault diagnosis and application of T-EMIO.