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Corona discharge is a typical discharge in gas-insulated equipment; however, the correlation between microscopic discharge process and macroscopic electromagnetic (EM) wave signals excited by discharge remains unclear. Therefore, this study innovatively employs the space current pulse as a bridge to reveal their relationship through the multi-scale simulation. First, the needle-plate discharge process in SF 6 gas is simulated based on a fluid dynamics model. Then, the effects of voltage, temperature, and the curvature of needle tip on the space current pulse are investigated. Lastly, the current pulses generated under varying conditions serve as excitation sources, and the finite-difference time-domain (FDTD) method is utilized to establish correlations between the corona discharge stages and discharge conditions and the amplitude-frequency characteristics of excited EM waves. The simulation results indicate that in the rising and falling stages of current pulse, the spectral energy is predominantly concentrated in the high frequency band (2.3–3.0 GHz) of the ultra-high-frequency (UHF) range, whereas the spectral energy constitutes the highest proportion within the mid-high frequency band (1.6–2.3 GHz) in the stabilization stage. As voltage, temperature, or the curvature of needle tip increases, there is a corresponding rise in the proportion of EM energy within both the low frequency band (0.2–0.9 GHz) and the mid-low frequency band (0.9–1.6 GHz), as well as in the mid-high frequency band; conversely, the proportion of energy within the high frequency band diminishes. The proposed multi-scale simulation method provides a novel way to obtain the characteristics of EM waves induced by partial discharge (PD) in gas.

The 2050 carbon‐neutral vision spawns a novel energy structure revolution, and the construction of the future energy structure is based on equipment innovation. Insulating material, as the core of electrical power equipment and electrified transportation asset, faces unprecedented challenges and opportunities. The goal of carbon neutral and the urgent need for innovation in electric power equipment and electrification assets are first discussed. The engineering challenges constrained by the insulation system in future electric power equipment/devices and electrified transportation assets are investigated. Insulating materials, including intelligent insulating material, high thermal conductivity insulating material, high energy storage density insulating material, extreme environment resistant insulating material, and environmental‐friendly insulating material, are categorised with their scientific issues, opportunities and challenges under the goal of carbon neutrality being discussed. In the context of carbon neutrality, not only improves the understanding of the insulation problems from a macro level, that is, electrical power equipment and electrified transportation asset, but also offers opportunities, remaining issues and challenges from the insulating material level. It is hoped that this paper envisions the challenges regarding design and reliability of insulations in electrical equipment and electric vehicles in the context of policies towards carbon neutrality rules. The authors also hope that this paper can be helpful in future development and research of novel insulating materials, which promote the realisation of the carbon‐neutral vision.

Insulation pull rods used in gas-insulated switchgear (GIS) inevitably contain the micro defects generated during production. The intelligent identification method, which requires large datasets with a balanced distribution of defect types, is regarded as the prevailing way to avoid insulation faults. However, the number of defective pull rods is limited, and the occurrence of different types of defects is highly imbalanced in actual production, leading to poor recognition performance. Thus, this work proposes a data preprocessing method for the insulation pull rod defect feature dataset. In this work, the YOLOv5s algorithm is used to detect defects in insulation pull rod images, creating a dataset with five defect categories. Two preprocessing methods for impurities and bubbles are introduced, including copy–paste within images and bounding box corrections for hair-like impurities. The results show that these two methods can specifically enhance small-sized defect targets while maintaining the detection performance for other types of targets. In contrast, the proposed method integrates copy–paste within images with Mosaic data augmentation and corrects bounding boxes for hair-like impurities significantly improving the model’s performance.

Gas-insulated power transmission lines (GILs) can replace cables and overhead transmission lines, playing an important role in DC transmission systems. However, the influence of surface charge accumulation on insulation reliability cannot be ignored as the operational voltage of the DC GIL increases. In this paper, the measurement methods for the insulator surface potential are summarized, including, dust maps, the Pockels effect method, and the electrostatic probe method. Then, a typical surface charge inversion algorithm is introduced. The main influencing factors of surface charge accumulation are analyzed, such as the applied voltage, insulation gas, insulator shape, and temperature. The charge accumulation pathway is revealed. Furthermore, methods for inhibiting the accumulation of surface charges and promoting the dissipation of accumulated charges are introduced to reduce the surface charges on insulators. Finally, the development direction of DC GIL insulators is predicted. We anticipate that the online monitoring of surface charge distribution, clarifying the percentage of charge accumulation pathways, and optimizing the insulator casting process will be the research directions for the insulator surface charge topic in the future. This article provides a comprehensive understanding of the surface charges of GIL insulators and a reference for the insulation design of DC GILs.

Air gap defects inside a spacer reduce its insulation performance, resulting in stress concentration, partial discharge, and even flashover. If such gap defects are located at the interface between the insulation and conductor, a decrease in mechanical stress may occur. In this work, a finite element method-based simulation model is developed to analyze the influence of gap defects on the electrical and mechanical properties of a ±320 kV direct current gas insulated line (DC GIL) spacer. Present findings reveal that a radially distributed air gap produces a more significant effect on the electric field distribution, and an electric field strength 1.7 times greater than that of the maximum surface value is observed at the air gap. The axial distribution dominates the distortion of the surface stress by generating a stress concentration region in which the maximum stress of the air gap is twice the pressure in the surrounding area.

An insulator surface charge may be responsible for flashover along the insulator surface. In this study, experimental investigations of post insulator surface charge are performed using a variety of voltage, gas type, and gas pressure conditions. Combining the model of surface charge transport, the dominant charge transition is revealed considering gas partial discharge. The results show that hetero‐polar charge accumulates near the high voltage electrodes on the insulator at one atmospheric pressure with an applied DC voltage ranging from −10 to −60 kV. The area ratio of the hetero‐polar charge increases from 23% to 53%. It also generates a reversed polarity of surface charges. Under −20 kV, the surface charge near the grounded electrode gradually becomes homo‐polar charges with the decrease of SF6 in 0.5 MPa SF6/N2 gas mixtures. In this case, the most dominant pathway for charge accumulation is through the insulation gas rather than the insulator. For the 20%SF6/80%N2 gas mixtures, homo‐polar charge speckles appear near the grounded plate electrode when the pressure of SF6/N2 gas mixtures decreases to 0.1 MPa. This means that the partial discharge occurs in gas side under a lower gas pressure. Refer to the presenting findings, the dominant charge transition on post insulators is provided as an important reference.

To suppress the charge accumulation on the spacer surface in direct current (DC) gas insulated transmission line (GIL) is an important and emergent issue for the development of a clean, safe and economic smart grid. A design method of the DC spacer is proposed, and a spacer prototype is prepared and evaluated both by simulation and type test. The DC withstand voltage test and polarity reversal test are performed using the new DC spacer compared with a commercialised 220 kV AC spacer. The simulation results indicate that the surface electric field and surface charge of the DC spacer are lower than those of the alternating current (AC) spacer under DC voltage. The test results verify that the surface flashover voltage of this DC spacer is higher than that of the AC spacer. The potential feasibility of the spacer design for HVDC is discussed. It is hoped that the content of this paper can bring new ideas in the development of HVDC gas insulated equipment.

Partial discharge (PD) detection is considered one of the most crucial and effective methods for identifying defects in electrical equipment. Consequently, investigating advanced and efficient PD monitoring techniques is essential for the development of gas‐insulated equipment (GIE) and the construction of ultra‐high‐voltage (UHV) networks. This paper first explores the causes and impact characteristics of various defects in GIE based on experimental results and simulation analysis. It then reviews current research on advanced PD measurement techniques, integrating acoustic, chemical and optical methods. The findings preliminarily demonstrate the unique advantages and applicability of the advanced methods for complex detection environments. Finally, this paper addresses the technical challenges and potential breakthroughs associated with these detection techniques. In this regard, this study aims to provide technical insights and research directions for defect detection techniques in UHV GIE.

Corona discharge is a typical discharge in gas-insulated equipment; however, the correlation between microscopic discharge process and macroscopic electromagnetic (EM) wave signals excited by discharge remains unclear. Therefore, this study innovatively employs the space current pulse as a bridge to reveal their relationship through the multi-scale simulation. First, the needle-plate discharge process in SF gas is simulated based on a fluid dynamics model. Then, the effects of voltage, temperature, and the curvature of needle tip on the space current pulse are investigated. Lastly, the current pulses generated under varying conditions serve as excitation sources, and the finite-difference time-domain (FDTD) method is utilized to establish correlations between the corona discharge stages and discharge conditions and the amplitude-frequency characteristics of excited EM waves. The simulation results indicate that in the rising and falling stages of current pulse, the spectral energy is predominantly concentrated in the high frequency band (2.3-3.0 GHz) of the ultra-high-frequency (UHF) range, whereas the spectral energy constitutes the highest proportion within the mid-high frequency band (1.6-2.3 GHz) in the stabilization stage. As voltage, temperature, or the curvature of needle tip increases, there is a corresponding rise in the proportion of EM energy within both the low frequency band (0.2-0.9 GHz) and the mid-low frequency band (0.9-1.6 GHz), as well as in the mid-high frequency band; conversely, the proportion of energy within the high frequency band diminishes. The proposed multi-scale simulation method provides a novel way to obtain the characteristics of EM waves induced by partial discharge (PD) in gas.

The China Spallation Neutron Source （CSNS） is the first accelerator-based multidiscipline user facility to produce pulsed neu- trons by tungsten target under collision of a pulsed proton beam with a beam power of 100 kW at a repetition rate of 25 Hz. In this paper, we focus on the physical design of CSNS target station and neutron instruments. Under optimized design, the flat tungsten target and the compact target-moderator-reflector coupling enhance effective cold and thermal neutron output from moderators. Three wing-type moderators supply four different characteristics of neutrons to 19 beamlines primarily for neutron scattering applications. Layout of neutron instruments are conceptually planned for total 20 beamlines, the configuration and specification have been determined for three day-one neutron instruments. All designs are optimized for the Phase I of 100 kW with a upgradable capacity to 500 kW.