Extra high‐voltage converter transformer resin impregnated paper (RIP) bushing is used as the outlet device of the converter transformer, its safe operation is directly related to the reliability of the power system. Under the long‐term effects of high current, strong mechanical stress and abrasion, the contact resistance of connection structure inside the bushing is prone to deteriorate. When the local overheating increases to a certain level, the insulation performance of bushing will decline and may lead to penetrating discharge. Therefore, it is vital to develop strategies for predicting the overheating fault of RIP bushings. In this study, firstly, one typical overheating fault of RIP bushing induced by the contact deterioration was diagnosed according to the fretting corrosive model and SF ₆ decomposition process. Secondly, using the three‐dimensional electromagnetic‐thermal‐fluid finite element method, the temperature distributions of RIP bushing under the different overheating degrees were simulated. Finally, based on the maintenance experience and simulation results, the diagnosis strategies were proposed. The diagnosis principle and prediction strategies were successfully helped to maintain the faulted RIP bushings and wall bushings before a destructive overheating accident could occur, which provide a basic reference for the fault prediction and improvements of relative standards.

Ultra high voltage (UHV) converter transformer valve‐side bushings are the key equipment indirect current (DC) transmission projects, and are subjected to high voltage and large current with large number of harmonics simultaneously. The electric field distribution of converter transformer valve‐side bushings is time‐dependent under DC voltage, polarity reversal voltage and actual voltage waveforms, and the electric and temperature field are coupling with each other in actual operation. The dynamic characteristics of the surface charges and the electric field distribution of China's first ± 1100 kV epoxy/paper – SF ₆ composite insulation converter trans former valve‐side bushing under 2 h DC withstand test voltage and polarity reversal voltage were analysed considering the natural ionisation, drifting, diffusion and recombination processes of positive and negative ions in SF ₆ gas and air. The time‐dependent electro‐thermal coupling field of the bushing under the actual voltage waveform in one cycle was obtained. The rationality of the simulation method adopted was verified through type tests of the UHV converter transformer valve‐side bushing. The simulation results of the paper can provide a theoretical foundation for the design of converter transformer valve‐side bushings and it is of great significance to ensure the safe operation of converter stations.

The metal dust moving inside the HVDC GIS/GIL will be easily adsorbed to the surface of the insulator and cause surface discharge. The study of the movement and adsorption characteristics of metal dust is extremely important. In this paper, NPLE image processing method is proposed that uses unified indicators to observe and count metal dust. The movement rules of metal dust particle groups inside DC GIS/GIL and the adsorption characteristics on the insulator surface are studied. The effect of metal particle traps on metal dust capture efficiency is explored. The results show that the range of concentrated distribution of metal dust inside DC GIS/GIL is basically stable, but there is a certain degree of randomness. The concentrated distribution range of metal dust is 148.1°, and the range where a large amount of metal dust is adsorbed on the surface of the basin insulator is 151.5°. The two ranges are very close. Assembling a particle trap can reduce the amount of dust adsorption by up to 99.86% in this experiment. Further simulation analysis found that areas with strong normal field strength on the surface of the insulator are prone to absorbing metal particles. The results can provide a basis for suppression and capture strategies of metal particles inside DC GIS/GIL.

Long-term operation of high voltage direct current at elevated temperatures can result in the accumulation of surface charges in DC gas-insulated transmission line (GIL) insulators. Such a phenomenon leads to localized electric field distortion, increasing the risk of surface discharge. The analysis of interaction behaviors between surface charge and space charge at interfacial domains of GIL insulators is a complex task, which requires a comprehensive understanding of physical mechanisms of the gas–solid interface charging. In this work, a two-dimensional bipolar charge transport and interaction (2D BCTI) model is established, with the consideration of both surface and space charge dynamics. Pulsed electroacoustic tests and surface potential measurements are conducted on DC GIL insulator materials under different electrical-thermal coupling conditions. Experimental results exhibit great consistency with the predictions from the 2D BCTI model. The local accumulation of space charge near interfaces has certain effects on surface potential distribution, which in turn influences charge injection behavior from electrodes. In comparison to traditional surface charge simulation models, the consideration of space charge–surface charge interaction behaviors proves to be essential for estimating the polarity and amplitude of surface potential distribution. This model holds promise for assessing charge characteristics in electrical equipment where direct measurement is challenging.