Abstract
The conductivity mismatch in the composite insulation of high voltage direct current (HVDC) cable accessories causes electric field distribution distortion and even insulation breakdown. Therefore, a liquid silicone rubber (LSR) filled with SiC nanoparticles is prepared for the insulation of cable accessories. The micro-morphology of the SiC/LSR nanocomposites is observed by scanning electron microscopy, and their trap parameters are characterized using thermal stimulated current (TSC) tests. Moreover, the dielectric properties of SiC/LSR nanocomposites with different SiC concentrations are tested. The results show that the 3 wt % SiC/LSR sample has the best nonlinear conductivity, more than one order of magnitude higher than that of pure LSR with improved temperature and nonlinear conductivity coefficients. The relative permittivity increased 0.2 and dielectric loss factor increased 0.003, while its breakdown strength decreased 5 kV/mm compared to those of pure LSR. Moreover, the TSC results indicate the introduction of SiC nanoparticles reduced the trap level and trap density. Furthermore, the SiC nanoparticles filling significantly increased the sensitivity of LSR to electric field stress and temperature changes, enhancing the conductivity and electric field distribution within the HVDC cable accessories, thus improving the reliability of the HVDC cable accessories.
Highlights
High voltage direct current (HVDC) transmissions have attracted increasing attention because of their many advantages [1,2,3], such as large capacity, long distance, fast and flexible power regulation, high transient stability, and low line loss
Cable accessories have always been the weakest part of HVDC cables because of their complex insulation structure, where most failures occur [8,9]
Under DC voltage, the electric field distribution of cable accessories only depends on the conductivity of the composite insulation and the interface space charge [10]
Summary
High voltage direct current (HVDC) transmissions have attracted increasing attention because of their many advantages [1,2,3], such as large capacity, long distance, fast and flexible power regulation, high transient stability, and low line loss. HVDC cables are indispensable to HVDC systems and have been widely used in asynchronous networks, underground power grids, and submarine transmission cables recently [4,5,6]. The operational safety and reliability of HVDC cables is very important for the stability of the HVDC transmission network [7]. Cable accessories have always been the weakest part of HVDC cables because of their complex insulation structure, where most failures occur [8,9]. Under DC voltage, the electric field distribution of cable accessories only depends on the conductivity of the composite insulation and the interface space charge [10]. The conductivity of XLPE is one or two orders of magnitude higher than SR insulation, which leads to electric field distortion or Materials 2018, 11, 403; doi:10.3390/ma11030403 www.mdpi.com/journal/materials
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