Search Results (27)

In direct-current gas-insulated transmission lines (DC GIL), complex heat transfer processes accelerate surface charge accumulation on insulators, causing local electric field distortion and elevating the risk of surface flashover. This study develops a three-dimensional multi-physics coupled mathematical model for ±200 kV DC GIL basin-type insulators. The bulk and surface conductivity of insulator materials were experimentally measured under varying temperature and electric field conditions, with fitting equations derived to describe their behavior. The model investigates surface charge accumulation and electric field distribution under DC voltage and polarity-reversal conditions, incorporating multi-field coupling effects. Results show that, at a 3150 A current in a horizontally arranged DC GIL, insulator temperatures reach approximately 62.8 °C near the conductor and 32 °C near the enclosure, with the convex surface exhibiting higher temperatures than the concave surface and distinct radial variations. Under DC voltage, surface charge accumulates faster in high-temperature regions, with both charge and electric field distributions stabilizing after approximately 300 h, following significant changes within the first 40 h. Following stabilization, the distribution of surface charge and electric field varies across different radial directions. During polarity reversal, residual surface charges cause electric field distortion, increasing maximum field strength by 13.6% and 47.2% on the convex and concave surfaces, respectively, with greater distortion on the concave surface, as calculated from finite element simulations with a numerical accuracy of ±0.5% based on mesh convergence and solver tolerance. These findings offer valuable insights for enhancing DC GIL insulation performance. Full article

Deformation monitoring of Gas-Insulated Transmission Lines (GILs) is critical for the early detection of structural issues and for ensuring safe power transmission. In this study, we introduce a rapid monocular measurement method that leverages deep learning for real-time monitoring. A YOLOv10 model is developed for automatically identifying regions of interest (ROIs) that may exhibit deformations. Within these ROIs, grayscale data is used to dynamically set thresholds for FAST corner detection, while the Shi–Tomasi algorithm filters redundant corners to extract unique feature points for precise tracking. Subsequent subpixel refinement further enhances measurement accuracy. To correct image tilt, ArUco markers are employed for geometric correction and to compute a scaling factor based on their known edge lengths, thereby reducing errors caused by non-perpendicular camera angles. Simulated experiments validate our approach, demonstrating that combining refined ArUco marker coordinates with manually annotated features significantly improves detection accuracy. Our method achieves a mean absolute error of no more than 1.337 mm and a processing speed of approximately 0.024 s per frame, meeting the precision and efficiency requirements for GIL deformation monitoring. This integrated approach offers a robust solution for long-term, real-time monitoring of GIL deformations, with promising potential for practical applications in power transmission systems. Full article

The advanced Gas Insulated Switchgear/Gas Insulated Lines (GIS/GIL) transmission equipment serves as an essential physical infrastructure for establishing a new energy power system. An analysis spanning nearly a decade on faults arising from extra/ultra-high voltage discharges reveals that over 60% of such faults are attributed to the discharge of metal particles and dust. While existing technical means, such as ultra-high frequency and ultrasonic sensing, exhibit effectiveness in online monitoring of particles larger than sub-millimeter dimensions, the inherent randomness and elusive nature of micron-nano dust pose challenges for effective characterization through current technology. This elusive micron-nano dust, likely concealed as a latent threat, necessitates special attention due to its potential as a “safety killer”. To address the challenges associated with detecting micron-nano dust and comprehending its intricate mechanisms, this paper introduces a micron-nano dust adsorption experimental platform tailored for observation and practical application in GIS/GIL operations. The findings highlight that micron-nano dust’s adsorption state in the electric field predominantly involves agglomerative adsorption along the insulator surface and diffusive adsorption along the direction of the ground electrode. The pivotal factors influencing dust movement include the micron-nano dust’s initial position, mass, material composition, and applied voltage. Further elucidation emphasizes the potential of micron-nano dust as a concealed safety hazard. The study reveals specific physical phenomena during the adsorption process. Agglomerative adsorption results in micron-nano dust speckles forming on the epoxy resin insulator’s surface. With increasing voltage, these speckles undergo an “explosion”, forming an annular dust halo with deepening contours. This phenomenon, distinct from the initial adsorption, is considered a contributing factor to flashovers along the insulator’s surface. The physical mechanism behind flashovers triggered by micron-nano dust is uncovered, highlighting the formation of a localized short circuit area and intense electric field distortion constituted by dust speckles. These findings establish a theoretical foundation and technical support for enhancing the safe operational performance of AC and DC transmission pipelines’ insulation. Full article

The overhead gas-insulated transmission line (GIL) in ultra-high-voltage converter stations, distinct from traditional buried pipelines, demands a thorough investigation into its seismic behavior due to limitations in existing codes. A refined finite element model is established, considering internal structure, slip between various parts, and the relative displacement at the internal conductor joint. Seismic analysis reveals the vulnerability of the GIL at the corner of the pipeline height change, with two failure modes: housing strength failure and internal conductor displacement exceeding the limit. Furthermore, the acceleration amplification coefficient of the support generally exceeds 2.0. Two retrofit methods, namely increasing the fundamental frequency of all supports and fixing the connections between all supports and the housing, have been proposed. The results indicate the effectiveness of both methods in reducing the relative displacement. Fixing all the supports effectively reduces the stress, whereas the other one yields the opposite effect. The seismic performance of a GIL is determined not by the dynamic amplification of supports, but by the control of relative displacement between critical sections, specifically influenced by the angular deformation of the pipeline’s first-order translational vibration mode along the line direction. Seismic vulnerability analysis reveals a reduction of over 50% in the failure probability of the GIL after the retrofit compared to before the retrofit, with the PGA exceeding 0.4 g. Full article

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. Full article

Metal particle contamination is an important reason for insulation failure of gas-insulated transmission lines (GILs). Particle trap is the common method for particle suppression. At present, research on the motion characteristics of metal particles near a particle trap and the optimization of trap parameters under AC voltage is insufficient. Based on that, firstly, a dynamic model of metal particles under AC voltage was established, and the motion characteristics of particles in front of the trap were studied, combined with experiments. Then, the influence of trap parameters on the capture effect was analyzed, and the optimization of the trap was realized by simulation. The results showed that, under AC voltage, the randomness of metal particle movement was strong, and the activity was low. The particles mainly moved away from the trap. Among the particles moving towards the trap, some stayed in front of the trap, and some fell into the trap from above. The thickness and height of the trap were the key parameters affecting the capture effect, and with the increase in height and thickness, the capture rate showed a trend of increasing first and then decreasing. The above conclusions can provide a reference for the optimization of a metal particle trap under AC voltage in engineering. Full article

Epoxy insulators are widely used in Gas-Insulated Transmission Lines (GILs), playing a significant role in electrical insulation and mechanical support. The metal particles generated during the production and operation of the equipment aggravate surface charge accumulation on the insulator, causing surface flashover. Therefore, it is necessary to study the suppression strategy of charge accumulation. In this paper, a downsized disc insulator was taken as the research object to investigate the effect of zoning coating on charge suppression with the presence of a linear aluminum metal particle under negative DC voltage. The zoning coating method was achieved by painting coatings with different conductivities in three areas on the insulator surface to regulate the charge. The inhibition mechanism of zoning coating on the charge accumulation in the presence of a linear metal particle was analyzed with the assistance of numerical simulation. The results showed that negative charges were accumulated in the nonplanar region as there was no metal particle, and the existence of metal particles led to the significant accumulation of positive charge speckles in the nonplanar region. The application of zoning coating could significantly inhibit the charge accumulation in the nonplanar area of the insulator and the charge injection from the grounded electrode to reduce the charge density. Under −25 kV, the maximum charge density on the insulator with the zoning coating was 48.1% lower than that without the coating, and the inhibition effect increased by 57.9% when the metal particle was introduced. This paper provides a new way to suppress the charge accumulation on the insulator surface. Full article

The movement of metal particles is effectively inhibited when a DC GIL’s (gas-insulated transmission line) electrode is coated. This article aims to study the problem of coating falling off during GIL operation and the change in the particle-inhibitory effect after coating ageing. A closed constant temperature heating platform and a particle motion observation platform in an SF₆ atmosphere were built. The epoxy resin coating was aged for 1200 h in an SF₆ atmosphere at 160 °C. Pull-off and particle-lifting experiments were carried out for the samples. The experimental results show that the adhesion of the coating changes from rapid decline to slow decline, decreasing by 35.5%. The lifting voltage of particle startup gradually decreased, and the inhibition effect on particle activity decreased from 45.89% to 35.7%. The coating mass loss rate and surface morphology were tested to explain adhesion decline. Then, the dielectric constant, electrical conductivity and adhesion work between the coating and the particles, which are the key factors affecting the lifting of the particles, were measured. Compared with the adhesion work, the dielectric constant of the coating has a greater impact on the starting voltage. The dielectric constant of the coating decreases by 24.07%, and the conductivity increases, which weakens its inhibition of particles. After ageing, due to the decrease in the dielectric constant and the increase in the conductivity of the coating, the inhibition of coating on particles is weakened. This paper reveals the changes in coating adhesion reliability and particle inhibition in DC GIL, providing guidance for using and improving the performance of coatings in practical engineering. Full article

China is taking initiative in energy transition to cope with the long-term controversy of its enormous energy consumption, aiming to use less carbon. Wind power, especially offshore wind energy, has become a prevailing alternative due to its low carbon emissions, renewability, competitiveness, and operation security. The layout of a transmission channel is a key consideration in marine project implementation. This paper investigates the technical characteristics, application status, and viable advantages of a conventional AC transmission, voltage source converter-based high-voltage direct current (VSC-HVDC) transmission, gas-insulated line (GIL) transmission, and hybrid HVDC transmission. A component-resolved evaluation model was proposed to estimate the costs to be incurred of four electrical transmission options for offshore wind power along the coast of Eastern China, with technical feasibility and economical considerations. Cost comparisons and component sensitivity analyses were developed with different transmission distances and capacities. Results suggest HVAC transmission and VSC-HVDC are the preferable solutions for present offshore wind farm development in Eastern China, and the economic potential of the hybrid HVDC makes it feasible for future deployment. Some conclusions can be applied in disparate regions across the globe. Full article

The temperature properties of real-type direct-current gas-insulated transmission lines (DC-GIL) with a basin-type spacer were investigated by the finite element method in this paper. A horizontally installed model was established and the temperature distribution was obtained with a 3D model. The specific heat capacity and thermal conductivity of the spacer were measured and applied in the simulation. The results show that the temperature of the convex surface was slightly higher than that of the concave surface. With an increase in the SF₆ pressure, the temperature of the spacer decreased, which can be attributed to the improvement of convection due to increases in the heat capacity per unit volume. With an increase in the ambient temperature, the temperature of the spacer increased linearly. The temperature difference between the inner and outer parts of the spacer increased with increases in the load current. Besides, an obvious increase in the surface electric field strength appeared under the influence of the thermal gradient compared to the results without the thermal gradient. Thus, special attention should be paid to the insulation properties of the spacer considering the influence of temperature distribution. This study evaluates both the thermal and insulation characteristics of the GIL along with the spacer under various conditions. Full article

Gas insulated transmission lines (GILs) are used in electrical systems mainly for power transmission and High Voltage substation interconnection. In this paper, we focus on the development of complex numerical tools for the optimization of gas insulated HVDC components by the estimation of realistic electric field distribution and the voltage holding of the designed geometry. In particular, the paper aims at describing the correct modelling approach suitable to study high voltage components in DC, considering the nonlinear behaviour characterizing the electrical conductivity of solid and gas insulators. The simulated field distribution is then adopted to estimate the voltage holding of the dielectric gas, with a convenient engineering technique, based on the streamer criterion. These two tools are integrated in an automatic optimization package developed in COMSOL^® and MATLAB^®, with the purpose of adjusting the critical geometry features, suffering from excessive electrical stress and possibly giving rise to electrical breakdown, in order to guide the designer towards a robust solution. Full article

Transient voltage generated in ultra-high voltage (UHV) transmission system has a severe impact on the insulation state of gas-insulated transmission lines (GIL). In order to monitor the transient voltage process occurring in UHV GIL during operation, this paper constructs a transient voltage ultra-wideband (UWB) online monitoring system based on capacitive voltage division. This system has been applied in an 1100 kilovolt (kV) GIL utility tunnel project. It can be used to analyze the characteristics of the recorded transient voltage waveforms for distinguishing different types of insulation failure. In this paper, through the case studies in time domain and time–frequency domain, the case of SF₆ gap breakdown and that of post insulator flashover have differentiated characteristics in instantaneous frequency. Additionally, a case of secondary discharge is successfully estimated through the time–frequency distribution of the transient voltage. In order to find the malfunctioning chamber of GIL rapidly, a two-terminal TW-based fault location method based on this monitoring system is developed in this paper. The case study validates the locating accuracy which directly support for shortening the maintenance time of GIL. Full article

This work presents a novel diagnostic method to localize Partial Discharges (PDs) inside Medium Voltage (MV) and High Voltage (HV) equipment. The method is well suited for that equipment presenting a bounded domain with fixed Boundary Conditions (BCs) such as Oil-Filled Power Transformers (OFPTs), Air Insulated Switchgears (AISs), Gas Insulated Switchgears (GISs) or Gas Insulated Transmission Lines (GILs). It is based on Electromagnetic (EM) measurements which are used to reconstruct the EM field produced by the PD and localize the PD itself. The reconstruction and localization tasks are based on the eigenfunctions series expansion method which intrinsically accounts for the physical information of the propagation phenomenon. This fact makes the proposed diagnostic method very robust and accurate even in real and complex scenarios. The promising experimental results, obtained in two different test cases, confirmed the ability and powerfulness of the proposed PD localization method. Full article

Gas-insulated lines (GILs) have been increasingly used as high-current busducts for high-power transmission. Temperature is one of the most important factors affecting the performance and ampacity of GILs. In this paper, an analytical method was proposed to determine the temperature of a three-phase high-current busduct in the form of a single pole GIL. First, power losses in the phase conductors and enclosures were determined analytically with the skin, and proximity effects were taken into account. The determined power losses were used as heat sources in thermal analysis. Considering the natural convection and radiation heat transfer effects, the heat balance equations on the surface of the phase conductors and the screens were established, respectively. Subsequently, the temperature of the phase conductors and the enclosures were determined. The validation of the proposed method was carried out using the finite element method and laboratory measurements. Full article

Due to the ever-increasing demand for electricity in the one hand and the environmental constraints to use clean energy on the other hand, the global production of energy from remote renewable sources, particularly from large hydropower plants and offshore wind farms and their connection to the grid are expected to grow significantly in the future. Consequently, the demand to carry this electric power by high voltage direct current (HVDC) technology will increase too. The most suitable HVDC power transmission technology to deliver large amounts of power, exceeding a capacity of 5 GW per bipolar system over long distances with lower losses is by using compact HVDC gas insulated transmission lines (DC GIL) and gas insulated switchgears (DC GIS) with rated voltage (maximum continuous operating voltage) of ±550 kV and 5000 A which are presently under development worldwide. Among the critical challenges for the development of these HVDC gas insulated systems, there are the epoxy cast resin insulators that are used to separate gas compartments also called spacers. Indeed, thorough research studies have been and still being carried out to well understand and clarify the electrical insulation characteristics of HVDC spacers using mainly cylindrical samples and small insulator models, where useful results have been obtained and proposed for implementation in real compact gas insulated systems. However, few practical investigations have been undertaken on real size spacers (product scale) to verify such research outcomes and validate the reliability of the spacers to collect experiences or for commercial use. This paper reviews the current achievements of real size HVDC spacers development. It describes the basic electric field calculation and spacers design, the verification of the insulation performance and validation testing. It gives today’s commercially available compact HVDC GIS/GIL and finally it presents the envisaged future research and development. Full article