Effect of Floating Metallic Particles in Pre-Breakdown and Breakdown Characteristics of Oil Transformer under DC Voltage

Contaminants in transformer oil insulation can float when meeting several conditions. Then, the presence of floating contaminants affects electrical characteristics insulation. Therefore, pre-breakdown (corona) and breakdown due to metallic particles would be investigated. This test used DC high voltage stress. A 56 Ω resistor was connected oscilloscope detect corona currents. The camera capture images light emission. In addition, electric field between electrode simulated. variables were particle size, including its shape, distance grounded electrode. experimental results show that average value inception inversely proportional size particles. peak current directly size. lowest found close electrode, but they not contact.