Influence of semiconductive nanoparticle on sulfur corrosion behaviors in oil-paper insulation

Copper sulfide deposition on oil-paper insulation will lead to insulation deteriorations or failures in power transformers. Recently, nanoparticles have exhibited great potential in improving dielectric strength of transformer oil. In this work, we aim to investigate the effect of semiconductive nanoparticle on the sulfur corrosion behaviors in the oil-paper insulation by adding certain amount of active organic sulfide. Thermal aging tests of paper-wrapped copper strips in both pure mineral oil and nanofluid were carried out. The corrosive characteristics of paper-wrapped copper strips were measured by scanning electron microscope (SEM) and energy-dispersive X-ray (EDX) analysis. The AC breakdown and lightning impulse breakdown voltages of two corroded oil samples were also tested. Experiments and analysis results indicate that the copper sulfide deposition not only changes the surface morphology of copper strips and insulation paper, but also reduce the dielectric strength of transformer oil. It was found that semiconductive nanoparticles can improve the partial discharge-resistance of corroded transformer oil. The obtained results are helpful for further understand the sulfur corrosion behavior in oil-paper insulation of power transformers.