In this paper, a Ni-doped MoS2 monolayer (Ni-MoS2) has been proposed as a novel gas adsorbent to be used in SF6-insulated equipment. Based on the first-principles calculation, the adsorption properties of Ni-MoS2 to SO2 and H2S molecules, the main decomposition components of SF6 under a partial discharge (PD) condition have been studied. The adsorption energy, charge transfer, and structural parameters have been analyzed to find the most stable gas-adsorbed Ni-MoS2. Furthermore, the density of states (DOS), projected density of states (PDOS), and electron density difference were employed to explore the interaction mechanism between SO2, H2S, and the Ni-MoS2 surface. It is found that the H2S molecule and SO2 molecule interact with the Ni-MoS2 surface by strong adsorption energy. Therefore, we conclude that the interaction between these two kinds of gases and the Ni-MoS2 monolayer belongs to chemisorption, and the Ni-MoS2 monolayer might be a promising gas adsorbent for the fault recovery of SF6-insulated equipment. Additionally, we have to point out that all of the conclusions only considered the final adsorption energy, the barrier in the transition state has not been analyzed in this paper.

In November 2017, the first ±1100 kV high-voltage direct-current power transformer in the world, which was made by Siemens in Nurnberg, passed its type test. Meanwhile, in early 2017, a ±1000 kV ultra-high voltage (UHV) substation was officially put into operation in Tianjin, China. These examples illustrate that the era of UHV power transmission is coming. With the rapid increase in power transmission voltage, the performance requirements for the insulation of power transformers are getting higher and higher. The traditional mineral oils used inside power transformers as insulating and cooling agents are thus facing a serious challenge to meet these requirements. In this review, the basic properties of traditional mineral insulating oil are first introduced. Then, the variation of electrical properties such as breakdown strength, permittivity, and conductivity during transformer operation and aging is summarized. Next, the modification of mineral insulating oil is investigated with a focus on the influence of nanoparticles on the electrical properties of nano-modified insulating oil. Recent studies on the performance of mineral oil at molecular and atomic levels by molecular dynamics simulations are then described. Finally, future research hotspots and notable research topics are discussed.