Interfacial microstructure and insulation properties of 500 kV EHVDC XLPE cable factory joint under different roughness and degassing durations

ACS Appl. Polym. Mater.

Meng

et al. 2022

Self Cite

This paper presents the influence of three different voltage stabilizers, 4-n-propylbenzoic acid, 2-methoxyphenylboronic acid, and 3-aminobenzoylmethylamide, on the insulation properties of cross-linked polyethylene (XLPE). The 1 wt % voltage stabilizers are blended with XLPE by a solution method, and then the samples are prepared via a hot pressing method. Electrical and physicochemical properties of the XLPE blends are analyzed by space charge, DC resistivity, DC breakdown strength, thermally stimulated depolarization current, Fourier transform infrared spectroscopy, thermogravimetric analysis, and differential scanning calorimetry experiments. It is found that the addition of the voltage stabilizers enhances the DC resistivity and DC breakdown strength of the XLPE, which also inhibits the accumulation of space charges in the XLPE. The results show that the XLPE blend with the addition of 4-n-propylbenzoic acid has the lowest conduction current and a 23.3% increment in the DC breakdown strength compared to that of the reference XLPE among the used voltage stabilizers. Moreover, it is found that the melting properties and thermal stability of the XLPE are not affected by the addition of the voltage stabilizers. The XLPE blend with 4-n-propylbenzoic acid exhibits a uniform trap depth distribution, which facilitates the migration of the space charge to the anode and reduces the electric field inside the sample bulk. Quantum chemical calculations demonstrate that the matching ability of the electron-withdrawing and electron-donating groups of the three voltage stabilizers effectively enhances the electrical properties of the XLPE. In contrast, the 4-n-propylbenzoic acid has the lowest unoccupied molecular orbital energy level, which can effectively buffer the high-energy electrons and increase the DC breakdown strength. A charge carrier transport mechanism is also proposed to explain the effect of the voltage stabilizer on the space charge movement in the tested samples.

Section: Resultsmentioning

confidence: 99%

Enhancement of Insulation Properties of Cross-Linked Polyethylene Utilizing Aromatic Voltage Stabilizers with Electron-Withdrawing and Electron-Donating Groups

Shi

ACS Appl. Polym. Mater.

Meng

et al. 2022

Self Cite

“…The derivative thermogravimetric (DTG) curves were obtained from the TGA curves, and the crystallinity χ and the lamella thickness L of the four samples can be calculated by the DSC curves by 17

χ goodbreak= \frac{△ H_{m}}{△ H_{0}} goodbreak\times 100 %

L goodbreak= \frac{2 σ_{e}}{△ H_{m}} \frac{T_{m 0}}{T_{normalm 0} - T_{m}}

where Δ H m is the enthalpy of melting of test material, Δ H 0 is the melting enthalpy at 100% crystallinity, σ e is the surface free energy per unit area of the basal face, T m0 is the equilibrium melting temperature corresponding to the infinitely thick crystal, T m is the melting point.…”

Section: Methodsmentioning

confidence: 99%

Voltage stabilizer and nanofiller in enhancement of insulation properties of cross‐linked polyethylene

J of Applied Polymer Sci

Hong

Dai

et al. 2022

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This paper investigates the influence of voltage stabilizer and nanofiller addition on the insulation performance of the cross-linked polyethylene (XLPE). The test samples of XLPE/stabilizer blends consisting of 1 wt% maminobenzoic acid, XLPE nanocomposites consisting of 0.5 wt% nano MgO and XLPE hybrid composite consisting of both voltage stabilizer and nanofillers were prepared. Various physicochemical and electrical properties were measured to analyze the performance of prepared samples. The obtained results show that the addition of nanofillers deteriorates the electrical insulation performance of the XLPE. On the other hand, the voltage stabilizer addition proves to be suitable for enhancing the electrical insulation performance of the XLPE. Meanwhile, the hybrid XLPE composites have shown medium behavior. The voltage stabilizer addition reduces, but the nanofillers increase the space charge density inside the XLPE compared to pure XLPE. It is also found that the dispersion of the voltage stabilizer in the material is uniform, whereas the nanofillers are aggregated. Furthermore, both additives slightly improve the thermal stability of the XLPE. The trap level theory based on quantum chemical calculation is proposed to explain the influence mechanism of the additives on the XLPE.

“…To avoid these problems, factory joints are a good solution. The preparation process of cable factory joints is fundamentally different from that of prefabricated joints . When preparing the cable factory joint, the main cable insulation is made into a symmetrical pencil tip shape, and then the surface is treated with sandpaper.…”

Section: Introductionmentioning

confidence: 99%

“…The preparation process of cable factory joints is fundamentally different from that of prefabricated joints. 33 When preparing the cable factory joint, the main cable insulation is made into a symmetrical pencil tip shape, and then the surface is treated with sandpaper. Next, the molten XLPE insulation is injected into the surface of the main cable insulation as return insulation with the help of a mold.…”

Section: Introductionmentioning

confidence: 99%

Spraying Core–Shell ZnO To Achieve High Insulation Performance for HVDC Cable Factory Joints

Meng

ACS Appl. Energy Mater.

Shi

et al. 2022

Self Cite

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.