The effect of adding electron-buffering voltage stabilizer (1 wt% maminobenzoic acid) on the electrical tree-induced degradation of cross-linked polyethylene (XLPE) was studied at high temperatures. The electrical tree inception, growth, and partial discharge characteristics were simultaneously analyzed at 30, 50, and 70 C, respectively. The results showed that the growth rate of electrical tree and partial discharge activity as well as the discharge repetition rate, significantly increased with the temperature for pure XLPE and XLPE stabilizer blend. However, the XLPE stabilizer blend exhibited higher tree inception voltage, lower tree growth rate, and partial discharge activity than pure XLPE. The addition of the voltage stabilizer reduced the carbon layer thickness in the tree channel and offered higher resistance to the electrical tree growth. Surface potential decay demonstrated that the voltage stabilizer addition decreased the trap energy level, but increased the shallow trap density of the XLPE. Quantum chemical calculations showed that the voltage stabilizer enhanced the ability to buffer the high-energy electrons in the XLPE. A high-energy electron buffering mechanism was also proposed to explain the effect of voltage stabilizer on the electrical treeing and partial discharge activity in the XLPE at high temperatures.

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The interface insulation plays a key role in the long-distance high-voltage direct current (HVDC) cables. In this paper, four core–shell ZnO suspensions formed by different alkane coating were prepared for spraying on the factory joint interface. The chemical, electrical, and simulation studies were performed on synthesized nanoparticles and factory joint samples. Results show that the alkane-coated ZnO exhibits a noticeable surface halo and the thermal weight loss ratio increases with the increase of the alkane chain. Moreover, with the increase in the sprayed C1-ZnO concentration (coated by trimethoxymethylsilane) from 0.005 to 0.1 wt%, the insulating properties of the samples show an increasing trend at first and then decrease. Furthermore, as the encapsulated alkane chain increases, a very small concentration of 0.01 wt% of ZnO suspension (C6-ZnO) coated with hexyltrimethoxysilane was found to be a highly effective spray reagent, which can significantly reduce the DC electrical conductivity, increase the DC breakdown strength, and remarkably inhibit the space charge accumulation at the interface. The microscopic characterization showed a good dispersion of nanoparticles at the interface. The space charge simulation and molecular simulation results elucidated the mechanism of the interfacial nanoparticles to suppress the space charge and insulation property improvement. This approach provides a new solution for realizing 500 kV or higher voltage DC cables to achieve long-distance connections and breakpoint repairs or improve other polymer interface insulation.

The potential decoration structures of Pd atom, Pd 2 cluster and Pd 3 cluster on the AlN nanotubes (AlNNTs) surface were initially studied. As the structure of Pd 2 decoration on AlNNTs is similar to that of two single Pd atom decoration, only Pd-AlNNTs and Pd 3 -AlNNTs were further analyzed. It is found that Pd atom and Pd 3 cluster preferred to adsorb on the surface surrounding N atom. Pd atom and Pd 3 cluster reduced the energy band gap, and increases the electrical conductivity of AlNNTs, especially Pd 3 decoration. The adsorption behavior, charge transfer, densities of states, projected densities of states, and molecular orbital analysis of AlNNTs towards four oil-dissolved gases, including H 2 , CH 4 , C 2 H 2 , and C 2 H 4 , were analyzed. These analyses indicated that Pd-AlNNTs and Pd 3 -AlNNTs showed strong interaction to four gas molecules. Pd-AlNNTs and Pd 3 -AlNNTs acted as the electron donators by transmitting electrons to the gas molecules during the interaction. According to the analysis of gas-sensing response, gas molecules adsorption on Pd-AlNNTs and Pd 3 -AlNNTs decreases the conductivity of the whole adsorption system.

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