Insulated Transmission Line Research Articles

Experimental study on dissipative characteristics of cathode plasma of coaxial magnetically insulated transmission lines based on microwave interferometry

Flash x-ray radiography is an important diagnostic in hydrodynamic experiments to provide fluoroscopic imaging of fast-moving dense targets. In order to obtain multiple images of an object at different times in an experiment, a flash x-ray accelerator is required to output multiple pulses. For the induction voltage adder (IVA) multi-pulse accelerator, it is important to study the effect of the cathode plasma generated by the front pulse in magnetically insulated transmission lines (MITLs) on the transmission of the subsequent pulses. In this paper, a coaxial MITL experimental platform based on the “QiangGuang-I” accelerator is established to study the dissipation characteristics of the cathode plasma, and its working condition is similar to that of MITLs in typical IVA accelerators. In the experiment, a stable magnetic insulation is formed in the coaxial MITL, and the current loss along the line can be ignored. The microwave interferometer is used to measure the evolution of cathode plasma density over time for hundreds of microseconds after the pulse disappears. The measurement results of microwave interference show that the line-averaged density of the plasma in the anode–cathode gap is above 1 × 1018 m−3, and the time for the plasma density to decrease to 1 × 1016 m−3 is about 600 μs. The expansion velocity of the plasma after a pulse is much lower than that during the pulse. In addition, the dissipation characteristics of the cathode plasma with different electrical parameters of the pulses are compared and analyzed.

Micro-discharge in GIS/GIL induced by scratch defect on the surface of insulation pull rods

Abstract The insulation pull rod (IPR) plays a crucial role in gas insulated switchgear (GIS) and gas insulated transmission line (GIL), which must withstand high impulse voltages to cope with frequent switching operations under working conditions. During the manufacturing process, micro-defects may occur on the surface of insulation pull rods, which may cause micro-discharge or even breakdown. It is difficult to carry out experiments to study the microscopic characteristics of the micro-discharge induced by micro-defects on the surface of the insulation pull rod. In order to study the relationship between the micro-discharge and the micro-defects. Firstly, the characterization of the scratch defect based on Micro-CT (micro computed tomography) and white light interference are presented. Secondly, a coaxial DC SF6 corona discharge model is established to obtain the curve related to the density of charged particles in SF6 and the electric field. Finally, we combined the reconstruction of the defect model in the first step with the curve obtained in the second step to simulate the micro discharge around the scratch defect, and provided the micro-discharge in pure SF6 caused by the scratch defect. The phenomenon of micro-discharge induced by the scratch of insulation pull rod is explained. The oscillation phenomenon of internal micro-discharge in scratch defects under high electric field background was discovered.

The angular distribution of characteristic parameters in eccentric magnetically insulated transmission lines

In pulse power modules designed with linear transformer driver (LTD) and magnetically insulated inductive voltage adder (MIVA) technologies, the phenomenon of electrode eccentricity in long-distance magnetically insulated transmission lines (MITLs) cannot be overlooked due to its impact on pulse power transmission. The paper conducts a theoretical analysis of the distribution of electromagnetic fields, vacuum impedance, and characteristic parameters such as self-limited flow in eccentric MITLs with respect to the angular direction. Additionally, it constructs an eccentric MITL model to validate the theoretical findings.

Novel GIL mechanical fault diagnosis method based on multi-sensor data feature fusion and TDEAVOA-ELM

The gas insulated transmission line (GIL), a crucial component of the power system, faces challenges in mechanical fault diagnosis including difficulties in quantifying sensor signal selection, balancing recognition accuracy, and model training speed. This paper proposes a GIL mechanical fault diagnosis method based on the feature fusion of multi-channel vibration sensor signals and an improved optimization extreme learning machine (ELM). Initially, three optimal signals are selected based on the correlation coefficients of multiple signals, and their time–frequency domain features are extracted. These features are then fused using neighborhood preserving embedding (NPE) and input into the improved optimized ELM model. The enhanced optimization algorithm reduces the likelihood of falling into local optima, thereby improving the model’s recognition performance. Experimental results demonstrate that this method effectively enhances the recognition accuracy of mechanical faults in GIL equipment and enables rapid diagnosis.

Unsteady heat transfer of long gas insulated transmission lines in tunnel: Model and analysis

The temperature of the cable core and cable casing is crucial for the safety and efficiency of the transmission system. Accurately predicting the distribution and variation of the transmission temperature field in the gas insulated transmission lines (GIL) tunnel is essential to ensure the long GIL tunnel transmission system's safe and stable operation. This paper addresses the challenge of calculating unsteady heat transfer flow in extra-long GIL transmission tunnels. The paper proposes a model, and a rapid solution method for extra-long GIL transmission heat transfer flow. In addition, the temperature variation during the operation of 1000 kV GIL has been analyzed. The results indicated that the conductor and cable casing temperature gradually increases and tends to be relatively stable with the operation time. The research results can provide theoretical basis and data support for the regulation of GIL tunnel transmission operation.

Insulation Coordination System 150kV Substation and Transmission Line against Lightning Surge Interference in a Nickel Smelting Plant

Insulation Coordination System 150kV Substation and Transmission Line against Lightning Surge Interference in a Nickel Smelting Plant

On the two-dimensional Brillouin flow

The Brillouin flow is a rectilinear, sheared electron fluid flow in a crossed electric field (E) and magnetic field (B), in the E × B direction with zero flow velocity and zero electric field at the surface with which the flow is in contact. It is broadly considered as the equilibrium electron flow in high power crossed-field devices including the magnetron and magnetically insulated transmission line oscillator. This paper provides an examination of Brillouin flow in two dimensions, in a cylindrical geometry where the anode radius changes abruptly at a single axial location, while the cathode surface has a constant radius. Our simulation confirms the proof that there is no equilibrium Brillouin flow solution for such a geometry. It further reveals that this change in the anode radius introduces novel bunching of the electrons within the Brillouin hub. This bunching occurs at low frequencies and is very pronounced if the Brillouin flow is from the small gap region to the large gap region, but is minimal if the Brillouin flow is from the large gap region to the small gap region. New insights are provided into the physical processes that initiate and sustain the bunching processes that are unique for a crossed-field diode, as compared with a non-magnetized diode. We argue that this enhanced bunching, and its concomitant formation of strong vortices, is not restricted to an abrupt change in the anode–cathode gap spacing.

Research on the Application of Multi-Physics Field Coupling Simulation in the Analysis of Temperature Field of 500kv GIS Circuit Breaker

Gas insulated switchgear (GIS) is a crucial part of any electrical infrastructure. Overheating the conductor on the GIS busbar would reduce the effectiveness of the insulating gas and shorten the life of the device. We then maximize output by fine-tuning the busbar's rotation angle, central distance, and conductor thickness. Dependable electrical systems always include gas insulated transmission lines (GIL) and gas insulated switchgear (GIS). Because of their reduced total cost and greater efficiency in terms of both space use and power transmission, GILs are gradually replacing conventional overhead lines for long-distance, high-power transmission. The reliability of GIL performance and the ease with which designs can be optimized necessitates research into their power loss and temperature profiles. The study found that the maximum temperature and power loss variances were approximately 70% attributable to differences in conductor thickness. By employing the aforementioned combination method (A1, B5, C5), energy consumption and thermal load in the GIS can be reduced. The research also shows that SF6 gas retains its outstanding insulating capacity after undergoing structural optimization. The calculation of the gas breakdown margin demonstrates this. In conclusion, the results of this study contribute to the understanding of heat transmission in three-phase GIS busbars and their optimization and engineering. Examining the temperature field of 500kV GIS circuit breakers, it highlights the value of multi-physics field coupling simulations in improving the reliability and performance of power system components, especially GILs. This is done so that power system components are more reliable and run more efficiently. Optimal heat transmission and other design considerations for three-phase GIS busbars are the most important takeaways from this research.

Energy harvesting technology for AC overhead insulated transmission line based on electric field induction

AbstractTo solve the problem of the energy harvesting (EEH) effect of the condition monitoring devices power supply on the transmission line is not ideal. The authors designed three kinds of EEH schemes based on AC electric field induction, which can effectively improve the output power of load power supply. The EEH principle of each scheme was analysed in detail, and the influence factors such as the shape of outer energy harvester, capacitance compensation and impedance matching characteristics were analysed. Finally, the experiment showed that 140.9 mW of power was obtained in direct‐mode field EEH when the line voltage level was 10 kV. The high‐potential field EEH mode obtained 4.1 mW of power. The harvesting effect of the inner energy harvester with the same potential as the aluminium wire was obviously better, and 30.7 mW of power was obtained. Finally, based on the third mode, when the load resistance was 2200 Ω, the rectifier received 23.7 mW DC output. The experimental results are in agreement with the theoretical analysis, which verifies the effectiveness of the electric field induction power supply technology.

Research on vibration response of 550 kV GIL isolation compensation unit against earthquake loading

To analyze the vibration response of Gas Insulated Transmission Lines (GIL) of urban power grid under different seismic intensity levels, based on the actual structure of the standard isolation compensation unit (isolation unit and compensation unit) of 550kV GIL, A fine 3D model of isolation compensation unit segment of 550 kV GIL was established, and the actual vibration response of each standard unit segment of GIL under different seismic conditions was studied by response spectrum analysis. This study clarified the action mechanism and law of GIL vibration characteristics under seismic conditions of urban power grids, provided the relative support for the research of shock absorption of GIL, and was great significance to the actual project of GIL.

Flexible smart surface coating for GIS/GIL epoxy insulators

AbstractA flexible smart coating with electroluminescence effect was designed and fabricated on the surface of gas insulated switch gear (GIS)/gas insulated transmission line (GIL) epoxy insulators based on two‐step curing process. As the AC voltage increases, the luminous area on the insulator surface expands from the centre to the periphery, and the light intensity shows a linear relationship with the applied voltage. Besides, the flexible smart coating can effectively identify the location of metal particle defects and the degree of electric field distortion. The flexible smart coating enhances the surface flashover voltage due to its higher dielectric constant. Simultaneously, metal particle contamination can substantially reduce the insulation performance of epoxy insulators, particularly when they are located near the high‐voltage side. It is hoped that this study can provide a reference for the smart detection of surface defects GIS/GIL basin insulators.

Profile of Inner Magnetically Insulated Transmission Lines to Minimize Energy Loss Under MA/Cm Lineal Current Density for High-Current Pulsed-Power Accelerators

Profile of Inner Magnetically Insulated Transmission Lines to Minimize Energy Loss Under MA/Cm Lineal Current Density for High-Current Pulsed-Power Accelerators

Application of Non-Contact Vibration Detection For Gas Insulated Transmission Line via Laser Doppler Vibrometer Technique

Application of Non-Contact Vibration Detection For Gas Insulated Transmission Line via Laser Doppler Vibrometer Technique

Environmentally friendly super-insulating material with three-dimensional nanoporous structure: A promising candidate for future gas insulated transmission lines and carbon sequestration

Gas-insulated transmission lines (GILs) play a pivotal role in facilitating the future long-distance transmission of power generated by renewable energy. However, the extensive employment of gaseous SF6 presents formidable obstacles to scaled application of GILs, due to its relatively low breakdown strength and substantial greenhouse effect. In this work, a fantastic phenomenon was discovered that the breakdown field strength of insulating gases can be significantly enhanced under the confinement of nanostructures, based on it, the starch/polyorganosiloxane biocomposite insulating dielectric (S/PBID) with three-dimensional nanoporous structure was designed and fabricated. Specifically, insulating gases (CO2, N2, SF6) composite with S/PBID, the breakdown field strength is significantly improved by 744.44 %, 520.74 %, and 310.95 % compared to the original gases, respectively. The relative permittivity of S/PBID (<2) is considerably lower than that of most existing insulating materials. Theoretical analysis suggests that the nanopores within S/PBID restricts electron multiplication and transport processes at the lateral scale, leading to a substantial enhancement in gas breakdown field strength. The nanoporous material is expected to be composited with atmospheric CO2 to overturn the conventional gas–solid composite insulation form of the GILs, thereby providing a novel insulation form of high-performance, environmental-friendly, and carbon sequestration.

The numerical simulation of a four-stage linear transformer driver module based on the Preisach magnetic core model.

The use of linear transformer drivers (LTDs) is widely considered the most promising technological approach for the development of future pulsed-power accelerators. In large-scale pulsed-power accelerators, abnormal conditions like switch prefire can occur frequently during tests and normal operations due to the presence of a large number of switches. The diagnosis of such faults based on signature waveforms requires further investigation. According to previous research, the characteristics of the magnetic cores greatly influence the fault waveforms. In this paper, a full-cycle mathematical model of the magnetic core is established utilizing a classical Preisach model based on experimental results. This model is coupled with the LTD circuit model in simulations, and simulation results are obtained under the condition of switch prefire. The simulation results are in good agreement with the experimental results from a four-stage LTD module with a sharing shell and de-ionized water insulated transmission line. The magnetization process of the cores is also determined under prefire conditions. Analyses of the magnetization process indicate that the completely demagnetized core shows high permeability under positive excitation and that the permeability abruptly decreases as the excitation is reversed. The hysteresis characteristics result in a phenomenon in which the output voltage in the prefired stage is almost unipolar. Finally, the features of the fault voltages captured in the experiments are also explained.

Insulation design of -800 kV gas insulation transmission line for negative ion based neutral beam injector

The high-voltage transmission line carries electricity, water, and gas for the high-potential components in the NNBI system. High voltage transmission lines used in -800 kV acceleration grade NNBI systems require the transmission of multiple high voltages of different voltage levels. Its insulation design not only guarantees the reliability of insulation but also requires a small occupation volume. The FEA method is used for insulation design of multi-conductor transmission lines. In the design of -800 kV transmission line, coaxial and non-coaxial structures are mainly considered. In the case of SF6 filling space, conductor radius and conductor position are the main factors affecting insulation strength. Both structures can make its insulation strength meet the requirements. However, it is found that the coaxial transmission line is more compact and concise when it meets the insulation requirements, but it is difficult to install and maintain.

Acoustic carrier signal transmission technology and its potential for in‐site monitoring of sliding electrical contact used in gas‐insulated switchgear/gas‐insulated transmission line

AbstractA wireless signal transmission technology based on acoustic carrier is proposed, which overcomes the limitation of electromagnetic signal shielding and shows great potential for in‐site monitoring of sliding electrical contact used in gas‐insulated switchgear (GIS)/gas‐insulated transmission line (GIL). Here, the state parameter of the sliding electrical contact is modulated onto the frequency domain of an ultrasound wave. As a mechanical wave, the ultrasonic wave is immune to electromagnetic shielding, so that it could carry the sensing signal to penetrate the metal shielding layer and transmit to the external terminals of GIS/GIL. The principle and signal modulation process of the acoustic carrier based transmission system have been demonstrated in detail. Both simulation and experiment have been conducted to analyse the system characteristics as well as optimise the system configuration. As a proof‐of‐concept application, the in situ and on‐line monitoring of the thermal rise of a slide electrical contact both in a current loading equivalent model and a prototype of GIS is demonstrated. Experimental results fit well with the physical process, and show a good measurement accuracy of 0.6% and temperature sensitivity of 400 Hz/°C.

Two-stage UHV GIL Fault Location Based on Ultrasonic Sensor Network

The failure of a long-distance Ultra-high voltage (UHV) Gas Insulated Transmission Line (GIL) during operation will cause great security risks to power transportation. How to locate GIL faults quickly and accurately and further carry out related operation and maintenance work is of great significance to the stable operation of the power grid. Based on this, this paper proposes a two-stage fault location method for UHV GIL based on an ultrasonic sensor network. In this method, ultrasonic sensors are configured in the shell of GIL to form an ultrasonic sensor network and internal faults are located by analyzing the signals collected from the network. The method is divided into two stages: 1) according to the collected signal data, the two sensors closest to the fault point are preliminarily identified, and then the fault point is roughly located, and obtain the data collected by the sensors; 2) we analyze sensor signal data, train and establish a network model based on recurrent neural network RNN for accurate fault location. The verification experiment shows that this method has fast location speed and high location accuracy, and can be effectively applied for quick maintenance, safe operation, and maintenance of GIL.

Efficient kinetic particle simulations of space charge limited emission in magnetically insulated transmission lines using reduced physics models

Efficient kinetic particle simulations of space charge limited emission in magnetically insulated transmission lines using reduced physics models

Study on sound transmission characteristics and positioning strategy of gas insulated transmission line shell

Gas insulated transmission line (GIL) is widely used for large-capacity power transmission in complex environment, and has the characteristics of long distance and totally enclosed structure. When the insulation fault occurs inside GIL, its metal shell structure makes it more difficult to monitor through optical, electrical and other physical quantities. Considering the rapidity and accuracy of positioning, the propagation of sound waves along the GIL sheath is a commonly used method in GIL on-site PD testing and running state online monitoring for fault positioning. This paper establishes a high-pressure GIL acoustic propagation simulation model based on pipe acoustics theory, analyzes the frequency dispersion and mode distribution of acoustic waves along the GIL shell, determines an appropriate fault location strategy based on the propagation velocity and attenuation of the selected acoustic wave mode, and carries out experiments to verify it. The results of the research show that the low order bending wave F(1,1) propagated along the GIL shell has good positioning characteristics, and the propagation velocity conforms to the dispersion curve distribution. By taking into account the attenuation and delay of the acoustic wave passing through epoxy insulators or expansion joints in the fault localization strategy, the localization accuracy can be improved by 60%. And this positioning strategy was verified to be effective in the GIL insulation fault localization test conducted in the field.