Simulation Analysis of EFDC of Oil-Paper Insulation under Typical Electrode Structures with the Influence of Harmonic Voltage

The primary sources of harmonic distortion in the new power system are a high percentage of access to power electronic equipment and a high percentage of renewable energy grid connections. These factors pose a major risk to the UHV converter transformer oil-paper insulation performance. However, the influence law of harmonic voltage on the electric field distribution characteristics (EFDC) of oil-paper insulation is still unclear; thus, the law of variation of spatial maximum electric field strength (SMEFS) under the action of harmonic voltage and the EFDC on the surface of oil-immersed insulating paper are investigated in this paper by building a two-dimensional simulation model of the electric field distribution of oil-paper insulation under ball-plate and cylinder-plate electrode structure. The results indicate that the two electrode structures' SMEFS are situated in the narrow oil gap between the oil-impregnated insulating paper and the high-voltage electrode; under the influence of the same harmonic components, the insulating paper's surface exhibits an inverse power function decay in the electric field distribution, with the cylinder-plate electrode decaying more quickly than the ball-plate electrode. Meanwhile, for both electrode structures, with the increase of the 5th and 13th harmonics, the SMEFS and the insulating paper surface field strength both increase linearly and are higher than that of the power frequency field strength, while for the 7th and 11th harmonics, the ball-plate electrode weakens the electric field and then increases it with the increase of the harmonic content, whereas the cylinder-plate electrode only increases the electric field.