Research on On-line Monitoring Data Fluctuation of Oil-paper Condenser Transformer Bushings during Precipitation

Transformer bushings are fundamental accessories of power transformers whose safety is extremely important. Traditional on-line monitoring technology on power frequency is widely applied within power grid to diagnose potential problems and prevent system failures in time. Usually, monitoring data of normal transformer bushings slightly fluctuate around a fixed value due to environmental condition such as temperature, ambient humidity and working voltage. According to warning strategy of on-line monitoring manufactures, monitoring data for bushings with good insulation condition should be less than a warning threshold. However, field operation indicates that on-line monitoring data, especially dissipation factor of normal transformers always experience a process of obvious abrupt rise and then gradual return to normal level during precipitation, which may mislead the diagnosis and even cause false alarm. Therefore it is meaningful to research on this fluctuating regulation and its mechanism. In this paper, the regulation and mechanism of on-line monitoring data fluctuation during precipitation is researched. Results of this research help better understand the evolutionary trend of on-line monitoring data and achieve an optimized monitoring and diagnosis method for bushing insulation conditions.