Abstract: The total electric field in HVDC wall bushing undergoes significant changes under corona discharge conditions. Therefore, an engineering-applied ±100 kV SF₆ gas-insulated DC wall bushing is selected as the study object. Using a field mill-type electrostatic field meter, the total electric field during both polarization under +90 kV DC voltage and subsequent depolarization after voltage removal are measured. The grounding tips are installed near the HVDC wall bushing flange to induce corona discharge, and the influence of tip lengths on the total electric field is analyzed. The results show that under normal conditions, the total electric field decreases rapidly initially and then stabilizes after 7200s with increasing polarization time, due to the accumulation of space charges on the surface. During depolarization, the total electric field decays approximately exponentially with a time constant of about 3×10⁴ s. As the tip length increases, the corona discharge transitions from smaller discharge magnitudes with higher frequencies to larger magnitudes with lower frequencies, resulting in a faster decrease rate and a lower stabilized value of the total electric field in the HVDC wall bushing. This study provides data support for elucidating the space charge distribution pattern on surface of HVDC wall bushings.

Key words: HVDC, wall bushing, SF₆ gas insulated, corona discharge, total electric field