Abstract
In order to study the influence of trap parameters on dielectric characteristics of nano-modified pressboards, pressboards were made using the nano doping method with different nanoparticle components. The dielectric characteristics of the modified pressboards were measured, and the trap parameters were investigated using the thermally stimulated current (TSC) method. The test results indicated that the conductivity initially declined and then rose with the increase of nano-Al2O3 content, whereas it solely rose with the increase of nano-SiC content. Moreover, the conductivity exhibited nonlinear characteristics with the enhancement of electric field stress at high nanoparticle content. The relative permittivity of modified pressboard declines initially and then rises with the increase of nanoparticle content. In addition, the breakdown strength of modified pressboards exhibited a pattern of incline followed by decline with the increase of nano-Al2O3 content, while it always declined with the increase of nano-SiC content. The analysis based on the energy band theory on trap parameters of the constructed multi-core model concludes that the nanoparticle components added in pressboard altered both the depth and density of traps. It is therefore concluded that trap parameters have significant influence on the dielectric characteristics of nano-modified insulation pressboard.
Highlights
As the major equipment used in high voltage direct current (HVDC) transmission systems, the converter transformer plays an important role in connecting the alternating current (AC) network to direct current (DC) network, and its reliability has direct influence on the operational safety of a power system
The oil-paper insulation is widely used in converter transformers and barrier systems as one of the most mature insulation methods
Based on the experimental study and modeling analysis on dielectric characteristics and trap parameters of nano-modified pressboards, the following conclusions have been drawn: parameters of nano-modified pressboards, the following conclusions have been drawn: (1) The depth and density of traps of pressboard can be altered by nano-modification
Summary
As the major equipment used in high voltage direct current (HVDC) transmission systems, the converter transformer plays an important role in connecting the alternating current (AC) network to direct current (DC) network, and its reliability has direct influence on the operational safety of a power system. The oil-paper insulation is widely used in converter transformers and barrier systems as one of the most mature insulation methods. The electric field is frequently concentrated to cause abnormal discharge even breakdown in oil-paper insulation structures [1,2]. In order to improve the dielectric performance of the insulation pressboard, much work has been done on this particular aspect in recent years [6]. Liao et al reported that nano-TiO2 and nano-AlN can be used to improve the AC
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