Metal-enclosed Transmission Line Research Articles

Gas Insulated Metal Enclosed Transmission Line (GIL) Seismic Response Analysis

The seismic response analysis of a 550 kV gas-insulated metal-enclosed transmission line (GIL) is carried out to address the seismic performance issues in the design of the GIL. Firstly, the GIL is modeled in three dimensions, and the pre-stressed modal analysis is conducted to obtain the vibration characteristics of the GIL structure. Secondly, the seismic response spectrum analysis is conducted according to the national standard, and the seismic characteristics are obtained to meet the requirement of resisting an earthquake of magnitude 9, but there are problems of relatively large stress distribution and small safety coefficient of the brace. Finally, it is proposed to change the cross-section of the bracket to strengthen the stiffness of the bracket to improve the seismic performance of the GIL equipment, and simulations are carried out to verify the results, which show that increasing the cross-section of the bracket can improve the seismic performance of the equipment.

Research on mechanical properties and impact resistance of origami-based metamaterial for GIL

Gas insulated metal enclosed transmission line (GIL) is a high voltage, high current power transmission equipment, widely used in large hydropower stations, large-scale energy hubs and other occasions. Aiming at the shock environment that GIL may face, such as earthquake shock and water flow shock, a mirror folded mechanical metamaterial based on the Miura-ori patterned is proposed in this paper, and its mechanical responses and shock resistance performance were studied through the numerical simulation and experiment. The results showed that compared with the single-layer folded structure, the mirror connection mode increased the plastic hinge in the deformation process of the structure, causing the better energy absorption. Moreover, the parameters research indicated that reducing the plane angle and increasing the dihedral angle can improve the energy absorption. Most importantly, the structure can achieve more than 60% energy absorption under the impact load, showing a good buffer energy absorption effect. This paper can provide some significant reference and guidance for the impact resistance of the GIL in the practical engineering.

Stories From China

Compared with traditional transmission technology such as cable and overhead line, gas-insulated, metal-enclosed transmission line (GIL) has advantages: high voltage level, large capacity, and small floor area. In addition, affected by structural characteristics of GIL, the operation is not sensitive to the surrounding environment. Therefore, it can be used in power transmission under complex conditions.

Finite Element Analysis and Experimental Study of Metal Shell of GIL

Mathematical modeling, finite element numerical simulation and experimental measurement of the stress-deformation distribution of the gas-insulated metal-enclosed transmission line shell were carried out. Also, Stress linearization analysis was used to analyze the maximum stress. The results show that the stress is linearly dependent on water pressure and the shell occurs elastic deformation without plastic deformation. The simulated maximum stress of 76.2MPa is fairly in good agreement with the measured one (69.9MPa). The stress linearization analysis results show that the shell well satisfies the environmental safety requirements. The experimental results are consistent with the finite element results.

Investigation of physical properties of epoxy-functionalized graphene nanoplatelets composite coatings on DC-GIL insulators by molecular dynamics simulation

Surface charge accumulation has become a major limiting factor for long-term operation of DC Gas Insulated Metal-enclosed Transmission Line (DC-GIL). It is an effective measure to restrain the surface charge accumulation by coating the insulator surface with nano-scale modified material. In this paper, epoxy based nano-composites were designed using molecular dynamics (MD) simulation. Epoxy resin and four kinds of graphene nanoplatelets (unmodified, hydroxyl functionalized, carboxyl functionalized and amino functionalized) composite models were established. Vital physical properties, including dielectric constant, thermal conductivity, mechanical properties, and glass transmission temperature were investigated under LAMMPS. The results show that the physical properties of the polymer can be improved at different levels by doping graphene nanoplatelets. Epoxy doped with hydroxyl functionalized graphene nanoplatelets (EP-GNOH) reduces dielectric constant by 25.9% which is the most important parameter to suppress surface charge accumulation with other physical properties improved. Epoxy doped with amino functionalized graphene nanoplatelets (EP-GNNH2) only has the maximum rise of thermal conductivity by 44.86% while other physical properties improves insignificantly. It is concluded that the selection of EP-GNOH as the dopant of epoxy resin is more suitable for the suppression of surface charge accumulation in practical engineering.

Reliability Prediction for GIL Equipment Based on Multilayer Directed and Weighted Network and Failure Propagation

As an effective alternative to the power cables and overhead lines in the electrical transmission networks, the gas-insulated metal enclosed transmission line (GIL) has been receiving ever-increasing usage worldwide. The GIL reliability, as one of the important characteristics of GIL equipment, is greatly determined by the processing technologies used in manufacturing, transportation, and installation stages, and failures caused by poor processing technologies can cause great damage to GIL equipment, which can further result in great losses to the electrified wire netting. Thus, it is necessary to study and accurately predict the reliability of GIL equipment to discover potential failure modes and take precautions before GIL equipment goes into operation. In this paper, a new reliability prediction model called the multilayer directed and weighted network (M-LDAWN) reliability prediction model is proposed to analyze and predict the GIL equipment reliability by concerning failure propagation and practical processing technologies. In the reliability prediction process, the reliability minimum cut sets triggered by substandard processing technologies are searched by the M-LDAWN model, and the increased failure rate of GIL equipment under each reliability minimum cut set is calculated considering the amplification and concatenation effects of failure propagation. Using the proposed reliability prediction model, the effects of substandard processing technologies on the GIL equipment reliability can be quantified, and the reliability fluctuation caused by them can be calculated. The effectiveness of the proposed framework is demonstrated on a practical GIL reliability prediction example.

Research on Induced Voltage and Current for Hybrid Transmission System Composed of GIL and Overhead Line

Abstract Gas insulated metal-enclosed transmission line (GIL) is a substitute for overhead line, which is used for power transmitting in complicated geographical or geological environment In order to satisfying the requirements of operation in maintained state, each side of GIL needs to be installed a grounding switch. For the hybrid transmission system composed of GIL and double-circuit overhead line, the whole overhead line will be divided into incomplete transposed/non-transposed parts due to connection of GIL. When one of the grounding switches of GIL closes, it can lead to much greater induced current in each grounding switch. The induced voltage and current for hybrid transmission system will also change because of different parameters between GIL and overhead line. Calculation methods of induced voltage and current for hybrid transmission system with GIL are presented in this paper. Then, calculation conditions for hybrid transmission system are analyzed based on these evidences. Su-Tong GIL pipe gallery project is taken as an example for simulation in ATP/EMTP. Compared with traditional transmission system with overhead line, much higher performance requirements for grounding switches of Su-Tong GIL pipe gallery project are necessary, especially for induced current.

The influence of surface charge accumulation on flashover voltage of GIS/GIL basin insulator under various voltage stresses

Under AC, DC and switching impulse voltages, the surface charges accumulated on the basin insulators of Gas Insulated Substation (GIS) or Gas Insulated Metal Enclosed Transmission Line (GIL) could distort local electric field and even reduce the surface flashover voltage. In order to quantitatively measure the influence of surface charge accumulation on flashover voltage of insulator in actual GIS/GIL apparatus, a high-precision 3D surface charge measurement platform and a reasonable model were established for flashover tests in reference to the insulation design and flashover properties of actual 220 kV GIS basin insulator. The surface charge accumulation dynamics and corresponding flashover voltages of the built models under different conditions were captured and analyzed. The results indicate that, as the density of accumulated surface charges increases under either AC, DC or switching impulse voltage application, the surface flashover voltage would decrease from 62.1 kV to 55.7 kV, namely a margin of 10.3% under AC voltage application. In the context of DC voltage, there appears a 22.8% flashover voltage drop, from 61.0 kV to 47.1 kV. While for the case of switching impulse voltage, the charge accumulation reduced the flashover voltage to 52.9 kV with a 13.6% decline from 61.2 kV. Based on the simulation and theoretical calculations, the ‘enhanced electric field zone’ was identified to justify the influencing mechanism of surface charges on flashover voltage. The research results could contribute to optimal insulation design and fault diagnosis of basin insulator in GIS/GIL.

Failure mode and effects analysis using Dempster-Shafer theory and TOPSIS method: Application to the gas insulated metal enclosed transmission line (GIL)

Failure mode and effects analysis (FMEA) as a useful tool in safety and reliability analysis to identify and eliminate known or potential failures from the process of product design, development and production has been widely used in a variety of industries. However, in traditional FMEA, there are two big flaws that of the acquisition and aggregation of experts’ diversity evaluations and the calculation of the risk priority number of failure modes. In our paper, an improved FMEA approach based on Dempster-Shafer Theory (DST) and Technique for Ordering Preference by Similarity to Ideal Solution (TOPSIS) method is proposed to dispose the flaws for improving the effectiveness of traditional FMEA. In the proposed FMEA approach, a new aggregation method on the basis of DST is introduced for aggregating various kind of evaluations, then the TOPSIS method is utilized to rank the failure modes according to the evaluations in relation to their severity, occurrence and detectability. Based on DST and TOPSIS method, the proposed FMEA approach can well capture and aggregate diversity evaluations of experts and rank the failure modes under a compromise way with the condition of various uncertainties. Finally, the proposed FMEA approach is applied to the hazard analysis of the failure modes identified in a gas insulated metal enclosed transmission line (GIL) and gets a good result which consistent with practical engineering background. By the analysis and comparison with other methods, we find that the proposed approach is more applicable in real application.

Research on experiment and simulation of charged spherical metal particle collision characteristic under DC electric field

Since there exist discharge problems in gas insulated metal-enclosed switchgear due to internal metal particle movement, the study in this paper thus, conducted an experiment and simulation research on the movement characteristics of particles, where the charge on particle and the collision recovery coefficient (CRC) was obtained. When the electrode is brass, the charge on the particle is close to the theory one and the CRC of aluminum, stainless steel and particle are 0.52, 0.75 and 0.79 respectively. Accordingly, the study, in order to take the particle charge and its collision process into consideration, established a particle movement model, and conducted a test has thereof. The results show that there exists excellent consistency between charge and its collision. According to the research, the relationship between particle size, material and collision characteristics was revealed. The result shows that under DC voltage the metal particle collision frequency decreases with the increase of particle size when the material of the particles is the same. The time difference between particles' moving to high voltage electrode and ground electrode becomes greater with the increase of the size of the particle. When the particle material is different, the collision characteristics are influenced by its density and collision recovery coefficient of restitution. Particle motion velocity loss becomes less before and after the collision when its collision recovery coefficient of restitution is larger. So the collision frequency is higher. The research results in this paper can offer some reference value to particles suppression measures in gas insulated metal-enclosed transmission line.