Effects of Temperature and Moisture Content on the Enhancement of Dielectric Loss of OIP Bushings Under Harmonic Voltages

With the increasing proportion of new energy sources in the grid and power electronic converters connecting renewable energy sources to the grid, the level of voltage harmonics is also significantly increasing. The harmonics not only degrade the power quality but also enhance the dielectric loss of the capacitive cores in the oil-immersed paper (OIP) bushings. The effects of moisture content and temperature on the bushings dielectric loss have attracted much attention, but the enhancement of bushing dielectric loss under harmonic voltages is still uncertain and more research is needed. Therefore, in this article, the effects of different temperatures and moisture contents on the enhancement of dielectric loss of the insulating medium of the bushings under harmonic voltages are considered. Taking the harmonic voltage generated by the converter valve as a reference, under different temperatures and moisture contents, the enhancement of bushing dielectric loss is analyzed. The bushing dielectric loss enhancement coefficient is proposed as an index describing the magnitude of the contribution of the harmonic voltages to the enhancement of bushing dielectric loss. The work in this article not only contributes to further understanding of the heating behavior and mechanism of dielectric loss in bushings under harmonic voltages but also provides an effective reference value for its accident analysis.