UHF Method on PD Detection and Breakdown Characteristics of Metallic Particle in Oil Insulation

Partial discharge is a discharge phenomenon in spark form between two electrodes between insulation, which should not be connected. When the phenomenon is sustained, it may cause insulation failure depended on insulation strength. The presence of contaminants decreases the dielectric strength of the insulation. The contaminant itself is produced by equipment that needs oil in its operation, such as transformers. The metal particle may float due to the random movement of the oil particles. This study conducts experiments in detecting PD with a UHF method by using the monopole antenna to analyze the effect of floating metal particles on the breakdown characteristics of oil insulation. HFCT will validate the detected signal. This study focused on two variables, the particle sizes and the distance between contaminant and electrodes. The test showed that the distance of the contaminant influences partial discharge occurrence. Breakdown voltage results on 5 mm and 10 mm distance were 66 and 76 kV. The size of the contaminant affects the value of inception and breakdown voltage of oil insulation. Average Breakdown Voltage of 5 mm and 10 mm contaminant at 10 mm distance were 69.5 and 71.4 kV. The bigger the contaminant, the higher the inception and breakdown voltage.