Analysis of Breakdown Characteristics of Sensing Optical Fiber in Oil under AC and DC Voltage Conditions

Exploring the influence of the sensing fiber on the oil gap insulation and understanding the influence of the sensing fiber on the internal insulation of the transformer winding turns is of great significance to promote the reliable application of the optical fiber built-in sensing technology in the field of transformer monitoring. In order to figure out the influence of the introduction of optical fiber on the insulation performance of the transformer under AC and DC voltage conditions, an experimental platform which suitable for the insulation performance test of fiber-transformer oil and oilpaper insulation structure was designed and built. Simulating the interaction between the actual built-in fiber and the insulation, and fully considering the relationship between the electric field and the insulation interface, the effect of the PVC temperature-resistant sheathed fiber on the insulation of the transformer was carried out under AC and DC voltage conditions. The results show that the optical fiber has a certain influence on the insulation inside the transformer, and the extent of influence is related to the type of voltage and the way of fiber arrangement. Under AC conditions, the average breakdown voltage of optical fiber in oil is higher than that of insulation oil, but under DC conditions it is lower than that of transformer oil. The breakdown voltage of the optical fiber under different voltages is lower than the breakdown strength of the oil-impregnated insulation paper.