During the long-term operation of converter transformers, the aging and decomposition of oil-paper insulation lead to the presence of cellulose particles in transformer oil, which affects the safe operation of the equipment. The motion characteristics of cellulose particles in short oil gaps and long oil gaps under a DC electric field are studied. The forces acting on a single particle, the aggregation characteristics of multiple particles, and the conditions for particle chain breakage are calculated and analyzed. An experimental platform is constructed to validate the conclusions. The results show that cellulose particles in transformer oil are subjected to the combined action of various forces under a DC electric field. Under the influence of the dipole force, multiple cellulose particles attract each other and form particle chains along the direction of the electric field. Changes in internal forces within the particle chain can cause the chain to break. The movement of particles in oil is closely related to the adsorption time of particle chains on the electrode surface and their movement time within the oil gap, which is affected by the resistivity, particle size, charge quantity, and external electric field intensity of the particles. In the experiments, particles form cellulose bridges in short oil gaps, while in long oil gaps, they move freely in transformer oil in the form of particle chains.

The gas state of the insulating gas significantly impacts the development and extent of the partial discharge (PD) in gas-insulated switchgear (GIS). Correlating these two factors allows for a more comprehensive diagnosis of insulation defects. At present, the ultrahigh-frequency (UHF) method has been widely used for PD detection in GIS. However, the measurements of the insulating gas's state in the field are primarily conducted offline or at gas valves, providing ineffective data for reference. To address this challenge, this article introduces a novel composite sensor capable of simultaneous UHF and gas state measurements. Building upon the disk-type UHF sensor structure, the composite sensor integrates a gas state sensing unit with the micro-electromechanical systems (MEMS) sensor as the core. A robust shielding shell is designed through finite element simulation to ensure the safety of the sensor, with the maximum induced voltage and electric field strength on the sensing unit measuring 0.28 V and 414 V/m, respectively. The average UHF measurement sensitivity of the composite sensor reaches 13.3 mm. In addition, the composite sensor exhibits low errors (±0.2 °C, ±3 kPa, and ± 10 μ L/L), high consistency and repeatability in temperature, pressure, and moisture measurement. Finally, the composite sensor has demonstrated its capability to simultaneously and safely detect PD signals and the gas state within GIS.

Optimized power system architectures and lighter weight are enabling considerations for the successful development of all-electric aircraft (AEA). In this article, a cross-redundant connection architecture and weight reduction solutions are investigated for a 90-seater full battery-electric aircraft from the perspective of high-power aviation cable. Design criteria of the power system architecture are introduced. Material selection, sizing, and weight estimation methods of cable for AEA are discussed by combining ground cable standards with aviation requirements. The influence of the conductor materials, voltage level, current, battery pack quantity, and operating temperature on cable evaluation is thoroughly discussed and analyzed. Weight comparison under two controversial voltage level options (800V and 3kV) is conducted. Comparison results show that the utilization of an aluminum conductor, PTFE insulator, and a voltage level of 3kV proves to be a preferable selection for current AEA medium and high voltage cables. Increasing the rating operation temperature to 120°C is a conservative and secure option. The layout of battery packs consistent with the quantity of distributed electric motors is preferable to achieve the lightest cabling system. This study provides a guideline for the cable sizing methods of high-power aviation cables and an optimized design solution for the power system architecture of AEA from the perspective of cable layout and weight assessment.