Abstract
The accumulation of space charge in polymer insulation limits the development of high-voltage direct current transmission and reduces the service lifetime of power equipment. The electrical properties of polymers are affected greatly by their crystalline morphology. In order to study the effect of silica on the crystalline morphology and space charge characteristics of low density polyethylene (LDPE), nano-SiO2/LDPE composites, micro-SiO2/LDPE composites, and nano-/micro-SiO2/LDPE composites were prepared by melt blending. The silica distributions were characterized by scanning electron microscopy. Fourier transform infrared spectrophotometry was used to determine the chemical structure of the silica, LDPE, and silica/LDPE composites. The crystalline morphology of the LDPE and composites was investigated with an atomic force microscope and by differential scanning calorimetry. The space charge distribution of the LDPE and composites was measured with a pulsed electro-acoustic system. The results show that the introduction of silica particles did not evolve the chemical structure of LDPE. Compared with that of pure LDPE, the crystallinity of the composites increases with the decrease in the grain size. Moreover, the silica/LDPE composites exhibit the ability to inhibit the space charge. The improvement of space charge in the composites was attributed to the traps existing on the interfaces between the silica particles and LDPE (crystalline and amorphous).
Highlights
With the development of energy sources, high-voltage direct current (HVDC) transmission has received special attention because of its particular features exhibited in transmission, such as fewer losses, ultra-distance, extreme capacity, and system stability
The development of HVDC transmission was limited, and the service lifetime of the power equipment was reduced by the accumulation of space charge in polymer insulation
In the Fourier transform infrared spectroscopy (FTIR) spectra of composites, no characteristic absorption peaks of the new chemical bonds appear, indicating that no new chemical bonds are formed between silica particles and polyethylene molecular chains
Summary
With the development of energy sources, high-voltage direct current (HVDC) transmission has received special attention because of its particular features exhibited in transmission, such as fewer losses, ultra-distance, extreme capacity, and system stability. The development of HVDC transmission was limited, and the service lifetime of the power equipment was reduced by the accumulation of space charge in polymer insulation.. The growth of space charges could lead to a regional high field due to distortion of the local electric field in the HVDC cable. The nanoparticles, with small size, large specific surface area, and high surface activity, create a large number of interface regions with the polymer. These interface regions greatly improve the electrical properties of the composite materials.. The nanoparticles in the polymer could affect the trap distribution, the carrier transport, and the electrical properties, such as space charge distribution, breakdown, electrical tree, and conductivity.. The space charge behavior is studied by the pulsed electro-acoustic (PEA) method
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