No abstract

The high thermal conductivity epoxy resin composites filled with inorganic filler can improve the low thermal conductivity of epoxy resin. However, a large number of fillers with high thermal conductivity will reduce other properties of the composites, which limits their use under high voltage, high temperature and strong mechanical force during operation. In this study, the dopamine-modified BN (DBN) and k-DBN (DBN modified by coupling agent KH-560) were prepared by employed the dopamine with catechol groups and coupling agent to modify boron nitride. The thermal conductivity, thermal stability, and dielectric properties of composites with different contents of modified fillers were studied. The results showed that surface modification improved the dispersibility of BN in the resin matrix and compatibility with the resin. Among BN/EP, DBN/EP, k-DBN/EP composites, k-DBN/EP composites had the highest thermal conductivity at the same number of additions. When the k-DBN/EP content was 30 wt%, the thermal conductivity of the composite was 0.892 W/(mÁK), which was an increase of 25.5% compared with the BN/EP composite. The appropriate amount of BN filling (20 wt%) can improve the breakdown strength of the composite material.

No abstract

An investigation into the effect of surface roughness on corona discharge intensity of long-term operating conductors is presented. The electric field distortion level was found to increase linearly with surface average roughness Ra. At the corona inception voltages, the ionization intensity ξ in the ionization zone was calculated, it would increase exponentially with the raise of Ra. As a result, the corona discharge intensity of long-term operating conductors was stronger, and the corona inception voltages were lower than those of the new conductors. The deviation of radio noise and audible noise was found to increase linearly with the raise of Ra.