Study on the Surface Charge Dissipation Characteristics of Epoxy Resin Modified by Dopamine Grafted Nano Boron Nitride under High Frequency Electric Stress
Li Zhihui1, Xie Zengqi2, Li Qingmin1, Dong Ziwei2, Wang Zhongdong3
1. State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources North China Electric Power University Beijing 102206 China; 2. Beijing Key Lab of HV and EMC North China Electric Power University Beijing 102206 China; 3. College of Engineering Mathematics and Physical Sciences University of Exeter Exeter EX44QJ United Kingdom
Abstract：Epoxy resin (EP) has excellent electrical and mechanical properties, commonly used as the main insulation material of high frequency power transformer. However, due to long-term work in a short rise time, high frequency voltage operation, the surface charge accumulation and dissipation process of the main insulation is affected under high frequency voltage. Surface charge is difficult to dissipate makes the degree of accumulation increased, resulting in increased surface charge density, easy to induce insulation failure. Nano modification is an effective means as to improve charge dissipation along composite insulation surface. In this proposed research, EP composites were prepared with dopamine modified nano boron nitride (h-BN). In this paper, a surface potential test system was first built to characterize the surface charge distribution of EP composites after high-frequency corona discharge, and then the isothermal current decay method was used to calculate the trap energy level distribution of EP composite insulating materials. The results show that the increase of the voltage frequency will lead to the increase of the initial potential and the accumulated charge density on the EP surface, and the potential decay rate first decreases and then increases, and reaches a minimum value at 10kHz. In addition, the high-frequency dissipation characteristics of the modified EP composites were also studied, and it was found that the dopamine grafting modification could effectively improve the high-frequency dissipation rate of the EP surface charge. When the doping mass fraction was 10%, the charge dissipation rate It reaches the maximum value of 62.15%, which is 19.41% higher than that of pure EP. The high frequency surface flashover characteristics of the two composite materials were further tested by the uniform boost method. The experimental results show that doping a certain concentration of BN nanofillers and BN fillers grafted with polydopamine can improve the creeping insulation performance of EP composites under high frequency stress, but too high doping content may reduce the surface charge dissipation rate, Increase the probability of creeping discharge. Taking the doping concentration of 10% as an example, the creepage flashover voltage of the P-BN/EP sample is 15.9kV, which is 14.73% higher than that of pure EP. The mechanism for performance improvement may include two aspects. On the one hand, the amino grafted on BN surface enhances the compatibility between the filler and the matrix, and the formed three-dimensional interconnected network broadens the charge dissipation path. On the other hand, the increased shallow trap density in the surface layer of the composite material facilitates the carrier to participate in the conductivity process through the tunneling effect, which boosts the carrier mobility. The presented results provide a referential basis for optimal design of the main insulation system of high-frequency transformers.
李志辉, 解曾祺, 李庆民, 董紫薇, 王忠东. 多巴胺接枝的纳米氮化硼改性环氧树脂绝缘表面电荷高频消散特性[J]. 电工技术学报, 2023, 38(5): 1116-1128.
Li Zhihui, Xie Zengqi, Li Qingmin, Dong Ziwei, Wang Zhongdong. Study on the Surface Charge Dissipation Characteristics of Epoxy Resin Modified by Dopamine Grafted Nano Boron Nitride under High Frequency Electric Stress. Transactions of China Electrotechnical Society, 2023, 38(5): 1116-1128.
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